[RETARGET] Support for 'revel debug' option.

Hi,

I'm new to Revel and quickly realized that having the option to use gdb would speed up my learning process.

I'm able to start gdb with my patch but I can't see the original source code while debugging. I tried to run the go compiler with -gcflags "-N -l" (http://golang.org/doc/gdb) but it does not help. 

I'm aware of https://github.com/robfig/revel/issues/33 but could not figure out what to do with '-srcPath'.

Any idea of what I should do next?

Thanks,

Ch. Bonello