Add Capistrano 3 support

Conflicts:
	lib/thinking_sphinx/capistrano.rb
Clean up Capistrano version-dependent recipe loading

Conflicts:
	lib/thinking_sphinx/capistrano.rb
Fallback to v2 recipe if capistrano is older than 2
Fix version detection, re-order v3 tasks
Removing symlink/share cap tasks. Not necessary.

Better to put your index files within shared and just leave them there. It's actually what's in the documentation, too.
Bringing real-time tasks into Cap v3 file.