Avoid Function#call unless context is provided.

Fix #1554.
Merge pull request #1557 from braddunbar/iterator-context

Avoid Function#call unless context is provided.
Bail out early when appropriate.
Merge pull request #1559 from braddunbar/property-guard

Bail out early when appropriate.
_.matches shouldn't throw on null values.
Tests also cover undefined.
Merge pull request #1568 from braddunbar/matches-null

_.matches shouldn't throw on null values.
Support arguments Object in _.isEmpty.

Fixes #1533.
Merge pull request #1573 from janraasch/feature/is-empty-arguments

Support arguments Object in _.isEmpty.
Tweak to taste.
Minor _.result optimization :)

Don't hate me

Mentioned this in #1515 a couple weeks ago
Merge pull request #1578 from megawac/result-optimization

Most minor _.result optimization :)
fixes #1575: underscorejs.org toc items way too wide
Remove changing nativeSome in tests

A side effect of this is that IE<=8 will pass tests more regularly
Merge pull request #1581 from megawac/patch-1

Remove nullifying Array.prototype.some in tests
Add a message to TypeError from _.bind
Merge pull request #1589 from mattrobenolt/patch-1

Add a message to TypeError from _.bind
Simply assert that a TypeError is raised
Merge pull request #1591 from mattrobenolt/better-test

Simply assert that a TypeError is raised
_.partition: include iterator and context arguments in the predicate