Changefeed docs.
Updates to changefeed docs.
Added args.md
changed -> to &rarr;
Style changes to args.md
Added document to args.md.
Ported `r.args` to other languages.
Added args.md for Python and JS.
Ported changes to all three languages.
Fixed js changes.md
Fixed languages for changes.
Fixed changes header.
Fixed JS comments.
Added io to JS changes.md
Remove  title from index.md
Merge pull request #349 from rethinkdb/michel_347_random

Remove `Description` titles in index.md
Merge branch 'mlucy_changefeed_docs' into v1.13
First pass at docs for issue #306
updating http docs and copying to ruby and python