add shipped and unshipped scopes to issues
add unship and delete to issues

Conflicts:
	config/locales/en.yml
allow for theoretical possibilty of getting shipped more than one issue and unshipping all of them
fix typo in en.yml
Filling out Issues Spec for unship and delete
more explicitly specify that unship is for the most recently shipped issue
adding model specs for unship
Merge pull request #61 from mcsweeneys/unship-and-delete

Unship and Delete Functionality