Make note on b-shim config
Add debug statements
Typo
Add debug statements
Flatten options arrays

Sometimes, using grunt's template function in the Gruntfile can result
in a confusing output where options contain nested arrays. Within the
task, nest arrays are never necessary, and will produce the wrong output
without a clear error.

This will just flatten all arrays so that we never encounter the problem
Check to make sure an external is actually a file

…and add some comments around the nested logic
typos