Allow passing the ignore option through to browserify
Revert "Allow passing the ignore option through to browserify"

This reverts commit 485118eacc96d4c0848360598951e71c9c9c50be.
Pass external, exclude and ignore all the same way. Test for ignore
Added test for 'external'
Added test for exclude option.

Slightly more complicated because the file needs to be executed to
see if errors are thrown properly.
Merge pull request #38 from cwacek/master

Allow passing the ignore option through to browserify