Improve loading times

[pslacerda]

Importing GromacsWrapper take seconds. Most of time was wasted in extracting the help for docstrings. Seems that both running the help commands and communicating to acquire the text takes almost 90% of loading times.

This screenshot was taken while profiling the gromacs package importing:

Albeit it is useful, isn't a such important feature and the library keeps running without it. Or maybe we can load it dynamically and make something similar to this:

class GromacsCommand(Command):
    @property
    def __doc__(self):
        if not self.__doc_cache:
            # load docstring
        return self.__doc_cache

Another option would be to reset GromacsCommand.__doc__ for each subclass. Now we can't simply set Trjconv.__doc__ = "docstring" because Command is an old style class (eg class C(object): pass) which disallow change members of object (ie __doc__). This change would allow it:

# doesn't inherit from object
class Command:
    pass

[orbeckst]

I like the idea of loading the doc strings lazily!

[pslacerda]

Done =)