In particular, this handles the case of trying to decode No Content
(204) responses.

[feature] NotFoundHandler on Subrouters is now called correctly.

Previously, concurrent calls to Client.Do would have data races writing
Client.Rate. Protect it with a mutex.

Resolves #253.

This test focuses on the feature of allowing sub-routers error handlers to precede the parents, rather than the code change required to provide this functionality.

Fix error when printing usage for multi-value arguments

Added support for version ranges with basic operators:

v, err := semver.Parse("1.2.3")
range, err := semver.ParseRange(">1.0.0 <2.0.0 || >=3.0.0")
if range(v) {
    //valid
}

We try to compare []strings, which are uncomparable types:

`panic: runtime error: comparing uncomparable type []string`

Add default values to usage

The value "all" is also possible for State. See https://developer.github.com/v3/issues/#list-issues
and https://developer.github.com/v3/issues/#list-issues-for-a-repository.

Check if the value isn't it's zero value and if not add a default value
to the usage text.

Add built ins to options in help output

Add `flushWriter` to `mutil.WrapWriter()`

This allows httptest.ResponseRecorder to be wrapped and still maintain
its Flusher compatibility

Adds help to the options in help output with an easy way to add more
built ins.

This only breaks in go tip.

Move package documentation to doc.go

This is in addition to the String method, which is oriented more towards
human debugging.

Fix bug with error not being written to stderr

Fix lint warning

[ci] Perform gofmt, go vet checks; use race detector during tests.

Only the usage message was written to stderr, the error was written with
the standard fmt.Println.

Write usage message to stderr on error

Remove excess trailing whitespace from Usage generation

When the parsing of parameters/flags fails eg. when a required flag is
missing, print the usage statement and error to stderr instead of
stdout.

This change augments the Travis CI build to perform:

- Check that all files follow gofmt style, including -s (simplify) option.
- Check that go vet does not report any problems.
- Use race detector when running tests, to ensure there are no data races found.

[test] Correct a printf verb type

% go vet
mux_test.go:1080: arg len(ancestors) for printf verb %s of wrong type:
int

Add coveralls badge

Add more tests for parser

add tests for usage info

add coveralls to .travis.yml