Saving lyrics

Hey again!

Here are the main changes:
<ol>
<li> When ```.cliaoke``` directory is created, create two subdirectories ```.cliaoke/songs``` and ```.cliaoke/lyrics``` for their respective files (songs are then placed in ```.cliaoke/songs``` and any subsequent lyrics that get downloaded later are stored in ```.cliaoke/lyrics```)
<li> When requested via ```lyrics.get```, first check to see if the lyrics are in ```.cliaoke/lyrics```
<li> When fetched via ```lyrics.fetch_lyrics```, save the lyrics in file in ```.cliaoke/lyrics``` with same name as ```*.mid``` file but with ```.txt``` extension.