Moved globals into closure to avoid conflicts
Removed jQuery dependency
Moved drawLine from inner function to closure

Should have done this to begin with. Previously, the function was getting recreated every time drawSilhouette was called.
Moved drawLine below dependent vars for clarity
'Fixed' some whitespace and semicolons

While semicolons are almost always optional in JS, most people say you should use them.
For more info on when and when not to use semicolons, see: 
http://stackoverflow.com/questions/2717949/when-should-i-use-a-semicolon-after-curly-braces
Added basic input check
Ran changes through Closure compiler (simple)
Merge pull request #1 from minrice2099/master

Various fixes and changes by minrice2099