Fixed location of sourceMappingURL, 2nd try

according to [Source Map Revision 3 Proposal](https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k) sourceMappingURL comments should be at the end of file.

Map files should be named *.js.map