Test cases for Nikola's ReST extensions
Implemented 'soundcloud' directive as a Directive subclass
Implemented the 'vimeo' directive as a Directive subclass
Implemented the 'youtube' directive as a Directive subclass
Renamed 'slides' class to 'Slides'
Removed trailing '/' in 'gist' url template

In GitHubGist.get_raw_gist(), a trailing '/' was causing the
request to return empty text, resulting in an empty 'noscript'
tag.
Removed 'code-block' directive, reimplemented 'listing'

Removed the 'code-block' directive in favor of the 'code' directive included
in docutils since 0.9. The 'listing' directive is now implemented using
docutils' CodeBlock.
Register ReST directives using their new names

Directives are now implemented as classes and their names became camel case.
Also we created two aliases for the 'code' directive (CodeBlock): 'code-block'
and 'sourcecode'.
Renamed pygments_code_block_directive.py to listing.py
Updated manual to reflect rst syntax changes

Reimplementation of Nikola's ReST extensions as Directive subclasses caused a
small syntax change. Options passed to the directive have now the ':key: value'
format instead of 'key=value'. Also the 'Code' section was updated to
communicate the switch to the built-in docutils 'code' directive.
Changes in pygments_code_block_directive.py are not needed anymore

Merge branch 'master' into rst-plugins-as-classes

Conflicts:
	nikola/plugins/compile_rest/pygments_code_block_directive.py
flake8 fixes
Merge pull request #388 from rbistolfi/rst-plugins-as-classes

Rst plugins as classes