test rubinius on travis too

Run the tests for rubinius on travis too.
Mark any html_attributes has held by a renderer as used
Add redcarpet_ prefix for stack_* functions
Ignored /tmp directory
Added support for org-table syntax

This just adds support for using a plus (+) as an intersection character
instead of requiring pipes (|). The emacs org-mode table syntax
automatically manages ascii tables, but uses pluses for line
intersections.
Removed and ignored Gemfile.lock

See http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile/
SmartyPants: Preserve single `backticks` in HTML

When SmartyPants is processing HTML (yes HTML, not Markdown), single
`backticks` should be left intact.  Previously they were being deleted.
Fix tests for libxml2 > 2.8
Added contributing file
Merge pull request #213 from brntbeer/contribution

Added contributing file
README language fixes

Fix some wording, grammar, etc.
Merge pull request #215 from mattr-/master

Trivial README Updates
Merge pull request #193 from rmm5t/ignore-tmp

Git ignore tmp directory
Merge pull request #172 from Gibheer/patch-1

Add Rubinius to the list of tested rubies
Merge pull request #194 from rmm5t/org-table-syntax

Add support for org-table syntax
Merge pull request #211 from strzibny/master

Fix tests for libxml2 > 2.8
Remove a deprecation warning and update Gemfile.lock
Remove Gemfile.lock

See
http://yehudakatz.com/2010/12/16/clarifying-the-roles-of-the-gemspec-and-gemfile
for the rationale

Fixes #196
ignore Gemfile.lock
Revert bcc1384 and 655a297

Will merge the PR manually so that the right person gets credit for the
changes.