[ALOY-1159] Update underscore library to latest version

Update underscore lib, per PR https://github.com/appcelerator/alloy/pull/578 Need to update both runtime and build-time versions of the lib.

Tim Poulsen 2014-10-14

In my testing, switching to Underscore 1.7.0 causes many of our tests to fail. This is possibly due to changes in the way the _.template function operates, though my workarounds for that didn't make tests work. Version 1.6.0 seems to work just fine. Possible options: * Switch to 1.7.0 and fix the underlying issues * Switch to 1.6.0 for the near-term, resolve 1.7.0 issues later * Switch to the lodash library instead
Tim Poulsen 2014-10-15

New PR https://github.com/appcelerator/alloy/pull/589 from [~elbow]
Tim Poulsen 2014-10-15

PR merged. Thanks [~elbow]! Functional test: Use the test/apps/models/todo app for testing, as models & collections rely on Backbone, which relies on Underscore. 1. Edit test/apps/models/todo/models/todo.js and un-comment the "for Backbone 1.1.2" block of code 2. Run that app. Add two to-do items. Mark one as done. Switch to the Active and Done tabs; the correct items should be shown on each page. Switch back to the All tab and both items should be listed.
Tim Poulsen 2014-10-23

Reopen to backport to 1_6_X branch
Tim Poulsen 2014-10-24

PR for 1_6_X https://github.com/appcelerator/alloy/pull/609 Functional test as above
Feon Sua Xin Miao 2014-10-28

PR merged.
Eric Wieber 2015-03-30

Verified fixed using: Titanium SDK 4.0.0.v20150325201813 Studio 4.0.0.201503271912 Appc NPM: 0.3.37 Appc CLI 0.2.204 Alloy 1.6.0-alpha2 Files have been updated to 1.6.0 and test cases listed above behave as expected.