Adding tests for .parent().
Fix bug in `parent` method

Ensure that the `parent` method operates over all elements in the set
and filters by the selector (when specified). Update methods that
utilize the method internally and documentation accordingly.
Implement $.parseHTML

From the [jQuery API
documentation](http://api.jquery.com/jQuery.parseHTML/):

> $.parseHTML( data [, context ] [, keepScripts ] )
> Parses a string into an array of DOM nodes.

The `context` argument has no meaning for Cheerio, but it is maintained
for API compatability.
Re-factor $.parseHTML to use $.load
Add missing unit test description
Implements contents()
Added mixed text test fixture
Add test cases for .contents()
Use _.reduce() instead of a manual loop in .contents()
Added newline at end of fixtures.js
Fixed a grammar mistake in fixtures.js
bump htmlparser2
Merge pull request #231 from jugglinmike/parsehtml

Implement $.parseHTML
removed redundant done from tests
Merge pull request #239 from khoomeister/clean-done-tests

removed redundant done from tests
Making next(All) and prev(All) on empty objects return empty object.
fixes #232
Merge pull request #237 from khoomeister/fixes-232

fixes #232
Merge pull request #229 from jugglinmike/parent-bug

Parent bug
Correct behavior of `Cheerio#parents`

When invoked on a top-level element, `parents` should return an empty
set.

Because a unit test for `Cheerio#parents` and the implementation of
`Cheerio#val` depends on the erroneous behavior, this code must also be
updated.