Make install

Automates the setup process. with this, you can do complete setup with 

$ git clone git://github.com/danohuiginn/todo.txt-cli.git
$ cd todo.txt-cli
$ sudo make install

Did this for my own benefit; if you actually want to include it, I'm happy to add documentation, make it more robust, etc. Currently works on ubuntu; assume it'll be OK on other linuxes, not sure about macs.