ref #22

The truth is, this change makes me sad.  It's a breaking change
for all clients and it adds more complexity to the library surface.  In
most cases, clients will simply drop the Response object on the floor
(which is actually all the library itself was doing before this
change... now we're just pushing that off to the client).

Initially, the Response object will be primarily of interest for
functions that return paginated result sets, since the Response.NextPage
field is the only way to know for sure if there are more pages that
should be fetched.  And this is really the cleanest way to get at that
data, so in that respect this change isn't so bad.

It's also worth noting that returning the raw Response object makes a
lot more since in a GitHub library than it may in others, given how
GitHub makes liberal (read: proper) use of HTTP request and response
headers.  Other APIs, like Google's various APIs for example, tend to
push things like pagination links into the response body.  While this is
certainly less of a purist view in terms of REST, it does make the lives
of client developers a lot easier, since then the response body contains
everything you need to know.  But whatever; this is how GitHub rolls, so
we'll roll right along with them.  (Somewhat ironically we are ignoring
the RESTful links in the GitHub response bodies, since we're actually
calling the API in an RPC style and don't do anything with those links.)

We still don't have an easy way to set arbitrary request headers, but
that's a problem for another day.

Fixes #22

This allows use to provide convenience methods for accessing the
paginations links that are returned in HTTP Link headers.  To expose
that, we'll need to return the Response from all API methods, which will
also allow users of the client to do any other kind of inspection of the
response.  This adds additional complexity to the API and will be a
breaking change, but seems to be the cleanest way to enable this sort of
thing.

Refs #22

This was done so that timestamp_test.go would have a corresponding file that
could easily be found. It did not make sense to move timestamp_test.go into
github_test.go if we are trying to move to a more specific source structure.

add quotes around json tag values in order to be compatible with
reflect.StructTag.Get

Repository service:
    ListLanguages   : Allows a user to list the languages for a repository
Activity service:
    ListStarred     : Allows a user to list the starred repositories for a user

Added a timestamp struct to handle different incoming time formats from
GitHub. Only modified the repo struct to reflect this new time struct
for now since it is currently the only location I am currently aware of
where this is an issue.

Issue: #1

Because the reset date is expressed as a Unix timestamp (rather than an
ISO 8601 timstamp), we can't directly unmarshal the JSON response.
Instead we have to do a little weird indirection to unmarshal it as an
int first, and then convert it into a proper Time object.

fixes #18

Since the library has received external contributions, Google is no
longer the sole copyright holder.  Update the boilerplate at the top of
each file to reflect that, and add AUTHORS and CONTRIBUTORS files to
track this information.

update Do() to update client.Rate on every API call. Fixes #12

This includes most API methods on pull requests (with the exception of
listing commits and the merge functions), as well as all of the methods
for pull request comments. (Fixes #13)

This also fixes a few oversights in the issues API.

This adds basic methods for working with issues, assignees, and issue
comments.  Issue events, labels, and milestones are not included in this
commit. (Fixes #7)

golint doesn't like the underscore in "url_"

This allows for making unauthenticated requests subject to your
application's rate limit (as opposed to the lower rate limit for
anonymous requests)

if we have an error reading the body of an API error response, still
return an ErrorResposne with the original response struct.  Simply
returning a string stating that we couldn't read the response body
doesn't give the caller anything actionable to work with or attempt to
process.

This now aligns with the (pretty strong) golang convention of the
package name matching the path basename

this is particularly important for methods like
Organizations.CheckMembership which return a 404 to indicate a
successful response of "false".

also minor doc cleanup

This commit adds the core library funcationality and establishes the
general calling style and testing structure.  Only a few GitHub API
methods related to organizations and repositories are included in this
first commit, mainly to cement the calling style.