Allow Karma to serve .map files by default

Fixes #68 

## Problem
.map files were not in the karma configuration for files that karma can serve. This causes sourcemaps not to work when running test watches in Chrome

## Solution
Add the proper config for *.map files.

## Testing
You can use react-tree or any TypeScript project to test.
- Run `gulp watch:test -c`
- Chrome will open and run the tests. Open developer tools and check the network tab. You should see some .map files are successfully requested.

@trentgrover-wf 
@evanweible-wf 
@charliekump-wf 

FYI - @patkujawa-wf