Configurable validation for list of endpoints

Hey I added the skipping configuration we talked about in this issue -> https://github.com/striglia/pyramid_swagger/issues/31

Let me know what you think :)
I don't believe this is valid INI format. See http://docs.pylonsproject.org/docs/pyramid/en/1.2-branch/narr/environment.html#pyramid-includes-vs-pyramid-config-configurator-include for an example of how to encode lists in the INI files.