Fix and cleanup [[DontEnum]] unit test.
Add `_.parseInt` and `_.runInContext` to the `underscore` build tests.
Add `contextProps` to make `_.runInContext` work in older IEs.
Tweak `_.parseInt` docs.
Adjust build for renamed variables and `_.runInContext` dependencies, and cleanup build.js and build/pre-compile.js.
Update builds and docs.
Remove unneeded `contextProp` value.