Merge pull request #207 from goffrie/sourcemap

Try harder to produce accurate source locations for async calls.
issue #207 - recompiled to fix paths
Add an option to change the output directory.
Add newlines to the ends of generated source files.
Use relative paths in source maps.

Also includes bonus fixes for source map error traces.
Clean up build.sh.
Support both file:line and file:line:col in firefox.

New versions of Firefox report the column number, so take advantage of
that.