Source maps support

[jackmcpickle]

Hi @johndwells is this easy to add?

It would be great so our logging tool rollbar.com can help point us in the right direction if an error occurs in our js.

[plankguy]

I run into a sourcemap problem where an ; is being appended at eof even when not being minified, therefore breaking sourcemap references.
The issue is:
https://github.com/johndwells/craft.minimee/blob/master/minimee/services/MinimeeService.php#L680
The if statement just needs to be moved up into the if($this->settings->minifyJsEnabled)

[plankguy]

Created pull request for change: #23