Add support for ROLEFILTER environment variable

ROLEFILTER is similar to HOSTFILTER. It basically takes a list of
roles and converts that to a list of hosts and acts as if you called
HOSTFILTER on those hosts.
git diff shouldn't modify its 'from' argument.
Merge pull request #37 from bpaquet/master

Fixes issue #36, ensures that `find_servers` returns an empty array when no matches are found.
Merge pull request #34 from jgr/master

Change to the diff method of git.rb to not modify its arguments. (Allows post-deploy hooks to see the accurate diff)
Merge pull request #32 from johnf/master

Add HOSTROLEFILTER environment variable, allows commands `$ ROLEFILTER=web cap <stage> deploy`
Merge pull request #39 from bpaquet/master

Issue #36 Fix problem in previous fixing : crash if find_servers is called with a ServerDefinition object
Task deploy:setup now respects :group_writable.
Make rsync copy non-excluded hidden files in the root directory
Add :on_no_matching_servers => :continue option for commands and tasks
added variable to be able to turn off recursive submodules update
:scm_verbose was living in opposite land. Have it enabled caused the git recipe to not be verbose.
Updated the verbose test.
Issue #59, when asked to teardown the connection to a server, if the connection is already dead (eg. due to a timeout or the server rebooting) resulting in an IOError, just remove it from the connection list
Merge pull request #58 from ThePixelDeveloper/patch-2

Updated the verbose flag test.
Merge pull request #52 from markjaquith/master

Make rsync copy non-excluded hidden files in the root directory. Affects :checkout, :remote_cache and :export deploy strategies.
Merge pull request #47 from marxarelli/master

Modified deploy:setup to respect :group_writable
Merge pull request #60 from willbryant/master

Fix for issue #59 regarding tearing down already-dead connections.
Merge pull request #57 from ThePixelDeveloper/patch-1

:scm_verbose was living in opposite land, fixed.
Merge all changes, and patch-up the test suite
Tweak version number handling, and update changelog and version number, releasing prerelease as I want the contributors to test theis before it goes mainline