Exclude phpunit.xml from git tracking
MDLSITE-2176 Improve the spam detection in forum posts

Only posts containing three or more URLs are now considered as spam and new
users are blocked from posting them. URLs produced by our file picker (for
embedded media) are excluded from counting.
MDLSITE-2176 Make the blocked post message less scary

Instead of throwing an exception, a bit "friendlier" error screen is displayed
now. As we can't really safely render the post properly formatted, it seems
better to just provide its original source (be it HTML, Markdown or whatever).
MDLSITE-2176 Do not penalise posts referring to other pages at our site

Credit goes to Dan Poltawski for suggesting this behaviour in the tracker.
Merge pull request #2 from moodlehq/MDLSITE-2176-false-positive

MDLSITE-2176 Prevent false positive forum spam detection