Merge remote branch 'markstory/whitespace'

Merge remote branch 'markstory/whitespace'

* markstory/whitespace:
  Updating documentation for whitespace trim tags.
  Making trim tags consume all whitespace, both horizontal and vertical.
  Adding additional test suggested by nikic.
  Making a capturing group non capturing, as the group isn't used.
  Moving newline trimming into the regexp used to match end of tags.
  Applying changes suggested by nikic to simplify how end of comments are processed.
  Fixing some whitespace.
  Fixing typo.
  Adding a bit of documentation for whitespace trimming.
  Adding whitespace trimming support to other tag types (comments, variables) Refactoring how whitespace trimming is done, and moving it into a separate option that is combined with other tag types. Adding more tests. Refs #284
  Fixing use of non-existent method name.
  Adding a test case for mixing {%- and %} tags together.
  Adding a test that uses tabs. Added a test for trailing tabs and -%} Refs #284
  Implementing {%- which trims non-newline whitespace preceding it. Refs