fix wrong sourceMapUrl 

fix #100
update source-map support
1、optimize handle regexp in utilities
2、separate the error handling when create source map.
add test case for source map
Merge branch 'patch-1' of github.com:neekey/less.js-middleware into neekey-patch-1
Tweaking and updating the tests and middleware for sourcemap support.
Updating the test trying to correct the error with sourcemap not being found.
Forcing the rewrite of the map file since it shares an artifact with the simple test.