Create paths based on filename if main contains more than one .js file

- Updated tests so they work with the new array conditions
- Added highstock and typeahead.js to tests
- Paths that would end up as 'typehead.js': 'path/to/typehead' now truncate down to 'typehead': 'path/to/typehead'. The user is warned that this is happening in the console output.
- The user is warned if one of their dependencies does not specify a js file in `main`.