remove .rvmrc
Merge remote-tracking branch 'upstream/master'

Conflicts:
	.rvmrc
remove un-exist MiniMagic#escape_string
use CommandBuilder#add_command instead of CommandBuilder#push when adding command options
remove tmp file
update version to 2.2.0
Merge pull request #20 from rdd-giga/master

Fix undefined method `CommandBuilder#escape_string` exception used with minimagic latest version