chore(.travis.yml): run tests on Travis-CI

Closes #10
Closes #11
chore(karma.conf.js): don't use DEBUG logLevel

It's noisier than is necessary...
docs(README.md): add Travis-CI status badge
docs(README.md): add CONTRIBUTING.md with contribution guidelines

And additionally, also update README.md.

Closes #20
docs(README.md): add note about CLA signature requirement

Closes #21
docs(LICENSE.md): license codebase under MIT

Per discussion, license has settled on MIT.

Closes #1
Closes #23
feat(InboxAPI): support setting HTTP headers for all requests, and withCredentials flag

These can be specified at runtime, or during initialization of InboxAPI. Ideally, one should use
the exposed API for doing this.

Closes #25
Closes #24
Closes #7
chore(.jshintrc): make jshint happy
feat(angular-inbox): support configuring HTTP headers and withCredentials

New methods are exposed similar to InboxAPI's runtime methods for specifying request headers and
the withCredentials flag, in order to support authentication.
docs(LICENSE.md): Extend copyright to authors of community contributions

See https://github.com/inboxapp/inbox-ios/commit/6b964601fd18eefdb9a2ccceadd0097c739ae329

This reflects a pattern common to open source projects, from Chromium to Node.js.

Closes #26
feat(InboxTag): add abstraction for querying by tag

Provides a simple abstraction for querying Tag objects, and querying for threads attached to those
tags.

It is not yet possible to query for messages attached to a given tag, as this is somewhat blocked
by a caching feature, but is forthcoming.

Closes #27
chore(InboxTag): make jshint happy
refactor(*): model API design after inbox-ios

This is a work in progress --- this will be broken apart into numerous commits later on before landing.

There are some breaking changes here, but the goal is to be a bit more unified with the IOS implementation.
WIP make jshint happy
WIP fix indentation
WIP: file upload capabilities
WIP: add INThread#messages() helper
WIP: fix build --- isArray needs to be declared and assigned early
WIP: fix examples to use the updated API
WIP: various fixes

- inheritance issue (can't depend on Class.prototype.super for deeply nested classes)
- date filtering and interpretation (for whatever reason, InboxApp times are in seconds since the epoch,
  while JS dates are milliseconds since the epoch).