Remove stray character
Remove stray blank lines
Add section about registering checkers
Add registering to the first example
Fix Sphinx package name

The real package name is Sphinx actually (with uppercase S), and we need
to use the real name to prevent Puppet from installing the package over
and over again.
Update tests for Rubocop 0.18
Fix syntax checker documentation test

Regression from 9b306f3
Delete excess trailing blank lines
Merge .PHONY statements
Add pre-push hook to run tests

Make sure that we never push with failing tests from master
Force re-provisioning of the VM in make vagrant-test
Fix Emacs dummy to parse the checking expression

Regression from 2a32223
Improve title of contribution guidelines
Add short role for Github links
Add missing reference target for installation instructions
Shorten the introduction of the manual
Shorten README and documentation frontpage
Clarify manual license blurp
Add manual license to README
Shorten the HTML title of the documenation