add commandline support (fix #31)

i had to make few minor changes on plugin_load. 
There was a problem with command line parser and nosetests - i think it will not work so i excluded parser from testing and no it is working right

Plugins exclusion is by class name or if you want i can change it back to exclusion by file name but i think this is better
this is good to be more informative,. just replace `imported_file.__name__` with `plugin_file`