Add support for --diff-filename=-
Add support for --diff-filename=-

This adds support for passing diff content on STDIN when using
--diff-filename=-. When specified, any input that is required (such as
authentication information) will terminate and inform the user they must pass
the appropriate information on the command line.

beol/rbtools,reviewboard/rbtools,datjwu/rbtools,reviewboard/rbtools,haosdent/rbtools,halvorlu/rbtools,clach04/rbtools_0.4.1,datjwu/rbtools,clach04/rbtools,beol/rbtools,reviewboard/rbtools,davidt/rbtools,bcelary/rbtools,halvorlu/rbtools,Khan/rbtools,1tush/rbtools,datjwu/rbtools,blair/pkg-rbtools,davidt/rbtools,haosdent/rbtools,halvorlu/rbtools,Khan/rbtools,davidt/rbtools,beol/rbtools,haosdent/rbtools,clach04/old_rbtools_0.3.2