bugfixes and optimizations

The original script did not work for me due to several bugs, for example spaces in author names, spaces in filenames, issues with `sed` on a Mac, and others. I fixed them and did some more cleaning up and optimizations.

I suggest to rename the project to `gource-live`, as the concept can be generalized to LIVE visualization of other VCS as well, with appropriate "feeder" scripts. I plan to add feeder scripts for other VCS, and improved `gource-live-*` wrappers with help and option parsing, etc, stay tuned.