Allow data attributes

Closes #57
add MIT license metadata when building gemspec

Hoe defaults to "MIT" anyways (for now), but it's best to explicitly
define the license here.
Add an encoding option to DocumentFragment#parse to mimic how Nokogiri behaves
Add new scrubber to remove unprintable Unicode characters, fixes #65
Merge pull request #61 from ktdreyer/gemspec-license

add MIT license metadata when building gemspec
Update license dates.
Merge pull request #62 from batter/add_encoding_arg_to_doc_frag#parse

Add encoding arg to DocumentFragment#parse to mimic Nokogiri
Updated changelog.
Fixing the hoe license declaration. Related to 40e1791.
Merge pull request #66 from swanson/fix-unprintable-characters

Add new scrubber to remove unprintable Unicode characters, fixes #65
Improving/fixing @swanson's unprintable chars scrubber.

Related to 538467e.
Setting up broader testing on Travis.
Further mods on the :unprintable scrubber.

Related to 538467e.
Adding :unprintable scrubber to the README
Adding a test case for ca618fc. Related to #64.
Merge pull request #59 from rafaelfranca/support-data-attributes

Allow data attributes
Parking jruby tests until we resolve https://github.com/flavorjones/loofah/issues/67
Add 1.8.7, since I think kaspth broke support.
updating CHANGELOG
Making the 1.8.7 build optional -- Nokogiri no longer supports it.