Add .NET config files as XML
Fix package.config to packages.config
 add pants BUILD file highlighting to languages.yml

the pants build tool uses python files named BUILD. This adds highlighting for them.
Reworking most heuristics to only return one match
Removing unused array of candidate languages.
Removing inconsistency of `find_by_heuristics` (was sometimes returning nil and sometimes returning and empty array)
Use heuristics earlier to inform the rest of the classification process
Moving comments
Bail earlier if the file is empty.

This will change behavior for empty files with unique extensions, returning nil instead of the language.
Remove more empty samples
remove reference to empty.js
Tests for BlobHelper#empty?
Add Language.find_by_extension
Add some tests for Language.find_by_extension
Fix docs
Allow extensions without a leading dot

This makes the API a little easier to use.
Merge pull request #1683 from github/find-by-ext

Extract Language.find_by_extension
Bumping to 3.5.0
Merge pull request #1694 from github/cut-release-v3.5.0

Bumping to 3.5.0
Make it safe to pass nil to Language.find_by_name/alias again

This restores compatibility with v3.4.x.