Add support for CommonJS, AMD, and global namespace usage methods.
Add jquery, underscore to package.json dependencies

This way, require('backbone') just works as expected.
Resolve jshint warnings.
Add test to ensure NestedModel is attached to Backbone when using require()

Introduces tape and a new grunt task, because mixing in this type of test
with qunit seemed to be a pain. This separates the two environments while
keeping consistent with a method to run tests.