Added command line utility.

Added a new target to the project. This is a command line utility
launcher for MacDown. The command line utility allows users to symlink
to their /usr/local/bin folder. In this way users can open files with
MacDown from the command line.
Move cmd source
Lower case target name for command line tools
Implement better file-opening utility

This implements a preference-based file-opening scheme. When the
CLI utility is run, all file name arguments are resolved to
absolute URLs and stored in a user default key *under the master
Macdown application's namespace*, and then launch MacDown.

Everytime MacDown is launched, it checks the aforementioned user
default key, and open any documents in it, creating non-saved drafts
if necessary (for non-existing documents). This mimics the expected
behaviours for "normal" editors, like VIM, nano, etc.. The user
default key is reset to nil after the documents are opened.

Closed #35.
Add @sorig to credits
Use CoreFoundation to maintain 10.8 compatibility
Set draft state first to silence warning
Code-sign CLI util on copy
Add version generation and print job
Make version outputs match
Cleanup
Do not require rm before re-building
Integrate GBCli
Rename task
Merge branch 'command-line-util'