Add support for task options and file globbing

This pull request introduces the separation of configuration options 
for mincer and source/destination file selection. The handling of 
options has been changed to follow the typical grunt task options 
pattern, the file selection has been rewritten to use the abstraction 
layer provided by grunt. This also enables support for globbing, multiple 
src/dest mappings and other goodies like dynamically building the files list.

Due to the major rewrite of the file handling this change is not backwards
compatible and breaks current task definitions. 

Before putting more work into this (updating docs etc.) I'd like to hear 
some feedback if this is something you'd be interested in merging.