Add em-http-request instrumentation support.
Attaches instrumentation directly to method instead of overwriting headers callback.
Typo.
Merge remote-tracking branch 'appneta/master'

Conflicts:
	lib/oboe/config.rb
Compatibility with Ruby 1.8
Order and eventmachine to list of instrumentations
Merge branch 'diogobenica-master'

Conflicts:
	Gemfile.lock