Fix vmg/redcarpet#337 by checking also for tabs
Merge pull request #338 from Juanxo/tabs-after-reference-colon

Fix vmg/redcarpet#337 by checking also for tabs
Fix missing period
Merge pull request #339 from kimisaraz/fix-missing-period

Fix missing period [ci skip]
Yield the humanized id of the headers

Using the `header` callback, it's now possible to get access to the
humanized generated id to easily keep tracking of the tree of headers
or simply handle the duplicate values easily.

Since the `HTML_TOC` and `HTML` objects both have this callback, it's
advisable to define a module and mix it in these objects to avoid
code duplication.

Resolves #310
Merge pull request #333 from vmg/headers-callbacks

Yield the humanized id of the headers
Improve Travis' feedback

Add 2.1.0 to the list of tested rubies but also keep ruby-head to be
sure to be compatible with the current trunk since Ruby moved to
semantic versioning, the release process is a bit faster.

Also simply test on the latest Rubinius version and allow failures on
it until we can find an appropriate fix for the code introduced in #333.

We should also rely on the travis_retry command when running bundle
install since the rake-compiler gem set up often generate a Bundler
error.
Remove entries about internal changes [ci skip]

The users don't need to know about this kind of changes
Use anchor instead of id for headers

Try to be consistent across the examples and the code and also try to be
a bit more descriptive ; anchor is more understandable than simply id.
Merge pull request #342 from vmg/improve-build

Improve Travis' feedback
Try to be consistent across the names and the code
Redcarpet v3.1.0
Properly define the header_anchor helper function

Prevents all the various segfaults we've seen since 3.1.0

Fixes #349
Update CHANGELOG for 3.1.1 release
Update the gemspec for the 3.1.1 release
Bump module version
Redcarpet v3.1.1
Remove the allowed failure for Rubinius

Since commit 7f82fb59945, everything is green! :green_heart:
Added 'Get started quickly' section
Remove a compiler warning

In 7b48ac95, the bufcstr prototype has been changed. This lead to a
warning since bufgrow is meant to change the allocated size to the given
buffer but the latter is a const.