Make CoffeeScript a dev dep, and loosen semver.

We only need it for development-time (e.g. pre-publish) compilation, and we
seem to compile fine with the current 1.6.3, so staying on top of bug fixes.
Loosen Streamline dependency semver spec.

We still need this to be a formal dependency since compiled Streamline files
still depend on a (minimal) Streamline "runtime".

We seem to both compile and run fine with the current Streamline 0.8.1, and
Bruno has been great about not introducing backwards-incompatible/breaking
changes to the *runtime*, so this lets us stay on top of bug fixes etc.
Loosen request dependency semver to ~2.9.

The current version is 2.27, and it works just fine.

There seem to be no breaking changes between minor version updates to request,
so this'll let us stay on top of bug fixes.
Tests: switch from expect.js to Chai.

Much more feature-rich. Also loosens semver spec for Mocha.
Merge branch 'feature/upgrades' into develop