Ruby strf snippet

strf snippet contains a template that should format time in the same way
as `Time.now` default output.
Merge pull request #283 from bsutic/ruby-strftime

Ruby strf snippet
fix css_block
Fix typo in ruby.snippets: snippets => snippets
Merge pull request #286 from igrep/correct-ruby.snippets

Fix typo in ruby.snippets: snippets => snippets
Merge remote-tracking branch 'upstream/master'