Support old-style extensions in RedcarpetCompat.

Also add in compatibility layer to translate some old extension names to their respective new names.
Ignore gh_blockcode and translate fenced_code to fenced_code_blocks
Use 'then' in `case when` statements.
Merge pull request #95 from bostonaholic/master

Markdown#render does not preserve encoding
Fix broken encoding test when input is not UTF-8

Fixes the failing test #test_should_return_string_in_same_encoding_not_in_utf8
in test/redcarpet_test.rb
Allow non-UTF-8 (or ASCII) encodings to be parsed
Handle all old to new extension name mappings

And ignore any mappings that are no longer supported.
Pass renderer options to renderer object as well
Fix loading paths in the Redcarpet binary
Merge remote-tracking branch 'lsegal/fix_encoding_failures'
Properly set the encoding for intermediate render strings
Backport: Skip UTF-8 BOM at the beginning of strings
Merge pull request #81 from lsegal/redcarpetcompat

Support old-style extensions in RedcarpetCompat.
Check that the Extensions object is a hash
bin/redcarpet: allow --<extension> options in ARGV
Separate between render and parse extensions in bin/redcarpet
Tag 2.1.0
Small documentation fix
Add :hard_wrap test
Make it clear that #render is an instance method