AUTOLINK_RE ruby 1.9 compatibility fix

ruby 1.9 complains about some regexp being too complex:

activesupport/lib/active_support/dependencies.rb:510: warning: nested repeat operator + and ? was replaced with '*'

not very helpful, eh?

after tracing the requires I simplified

(?:/(?:(?:[~\w\+@%=\(\)-]|(?:[,.;:'][^\s$]))+)?)* # path

to

(?:/(?:[~\w\+@%=\(\)-]|(?:[,.;:'][^\s$]))*)* # path

this stops the warning, and should be equivalent (I think so and there no test failures).