Use relative URLs, not absolute.

This helps if somebody would fork a GitHub repository, as the links
now lead to files in fork, not files in original repository. Also, it
makes more sense when reading Markdown files locally.
Add hint on how to rebake posts
Refactored duplication in user action
Allow Chinese characters in Topic titles
Merge pull request #905 from chrishunt/chrishunt/allow-chinese-titles

Allow Chinese characters in Topic titles
Merge pull request #904 from janjiss/master

Removed code duplication on UserAction model
Simplify user action make it more idiomatic
Merge pull request #895 from GlitchMr/readme-links

Use relative URLs, not absolute.
Merge pull request #845 from Supermathie/rebakedocs

Add hint on how to rebake posts
Merge branch 'master' of git://github.com/discourse/discourse.git
Merge branch 'master' of git@github.com:9034725985/discourse.git