make sure that we only try to compile .erl files
refactoring load_all_modules
Show a sensable error on loading with an error

we were getting a badmatch if there was a compile error on loading we
now get a message like this, which is much easier to read than.

````
(erlang_ci@sag)1> 12:54:09.915 [error] Load Module Error lib_modules : [{"/home/zkessin/Documents/erlang_ci/src/lib/gh_util.erl",[{30,erl_parse,["syntax error before: ","forks"]}]}]
````

fixes ChicagoBoss/ChicagoBoss#370