Add missing test module

The `is` test file was not included in test/index.html, and so its tests were
not run. This commit adds it.
package.json: alphabetize dependencies
Merge pull request #342 from davidchambers/dependencies

package.json: alphabetize dependencies
Merge pull request #341 from markprzepiora/run-is-test

Add missing test module
some little doc fixes
Add support for headless testing using Testem

The test suite can now be run by installing testem globally and running
"testem" (or "testem -l phantomjs" if you have phantomjs installed to run tests
headlessly).

If you don't want to (or cannot) install testem globally, you can run
"./node_modules/bin/testem" instead.

These commits:
- Replace inline require shim with a file
- Add testem and configuration
- Add section to the README describing how to run tests