Wait for a numeric on IRC notifications

Code originally by Nick Markwell (@duckinator), ported to the current
codebase by me. This is a port of the code in travis-ci/travis-core#56.
Remove unnecessary line

If we refer to @numeric_received when it's not initialized, we'll get
nil back, and since we just need a falsey value, that's enough.
remove the log services as they now live in travis-logs
no need to register something which no longer exists
unused log service removed
removed unused job and build archive api payloads
remove the autoload for update_log
remove the spec for the update_log service
Delete only addons which are not whitelisted

We delete addons for remote pull requests for security, but not all
addons are unsafe. firefox and hosts are perfectly fine to be left in
config.
Underline link to build.
Remove require for now-deleted async file in travis-support.
Merge branch 'hh-irc-wait-for-numeric' of git://github.com/henrikhodne/travis-core into henrikhodne-hh-irc-wait-for-numeric
Add a timeout around wait_for_numeric.
expose github_id to worker
Merge pull request #259 from travis-ci/dont_delete_all_addons

Delete only addons which are not whitelisted
also stub github_id on repo
fix tests
Merge pull request #260 from travis-ci/rkh-worker-github-id

add github_id to payload sent to workers
Use int cast instead of floor and float cast.

This potentially has performance issues that cause trouble.
handle server error when fetching .travis.yml better