Add simple about dialog

Uses a builtin about dialog provided by 'wx'.
TODO: add cpymad version information.
Merge branch 'master' into about-dialog
Use ez_setup.py to bootstrap dependency on setuptools

See: https://pythonhosted.org/setuptools/setuptools.html#using-setuptools-without-bundling-it
Add metadata in __init__.py
Add madgui/LICENSE file

In order to include the license text in the actual application.
Merge branch 'metadata' into about-dialog
Use the metadata for the about dialog
Use the included full LICENSE text in about dialog
Merge pull request #67 from coldfix/about-dialog

Add about dialog