Fixed LOTS of spacing issues

Switched from tabs to spaces
Added check for note directory for all functions

This method sucks. Need to write a main function that calls further down, which
unfortunately will present a three-layer system, but it's better than copying
and pasting code seven times.
Fixed license header
Added LICENSE text for GPLv3
Conversion to MVC methodology

Created main function which acts as a proxy between the "backend" functions and
the "frontend" functions that the user interfaces with.

Renamed old "frontend" functions to *_sys, which are now called by main.

Created new "frontend" functions which are nicely named so the user can call
them easily.
Added check for git

Notifies user if git is not installed. It still works, but has slightly reduced
functionality as notes cannot be versioned.
Removed all refs to note_dir_exists

Removed this function in commit 848b14b776bfd4df4b18496d279a5e91765c237e as the
functionality is handled in the main function now.
Minor tweaking of git not-found error text

Just added some new lines. Updated the text a bit and added NOTE ot the
beginning to make it stand out a bit more.