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.
simplify, clarify TextSentinel

codeclimate pointed this out. I agree it is better
to simplify and reveal intentions.
small refactor of RateLimiter for clarity
extract TopicNotifier class from topic
minor refactorings
Make pry a bit more useful
Extract Topic#posters_summary
Remove unused parameters from posters_summary
Add hint on how to rebake posts
Sliding window rate limiting

Switched the algorithm to use a circular buffer
based on a redis list
Add Post#is_first_post?

We should be able to ask a post if it's the first in a topic
Add Topic#max_post_number to find max post number
Add Topic#url for determining url for a Topic
Add test to verify posts are moved in transaction
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.