Merge branch 'release/v2.2'
Invoke observation block for NSnotification right after calling the method

The observation block for NSNotification will be invoked immediately during the
call of an observation method `-observeNotification…`. In this initial
invocation, the "notification" block parameter is nil.
Added a .gitignore.
Merge pull request #6 from redhand/master

Added a .gitignore
Fix possible crash when removing observations on foreign object.

I was mutating enumerated set, so now I create a copy of it.
Merge branch 'master' into develop