CLN: clean up parser options

[cpcloud]

Also add a test to make sure that the C parser options validation is actually
covered

example travis fail:

https://travis-ci.org/pydata/pandas/jobs/12171563

explanation (for the record):

if you print out options before this commit you'll see that they are all overwritten with a single value. Whatever this value is will depend on how the _parser_defaults dictionary happens to be ordered (which is random because of hashing).

This caused a bug because the value of value is retained from the loop over _parser_defaults, and default is not reassigned in the two loops that follow the loop over _parser_defaults, so all the values end up being the same as the last argument that was iterated over from _parser_defaults.

magic explained 🎉

[jtratner]

Great work catching this! 👍

[cpcloud]

i'm not sure about this factorize argument ... now that i think about it i think it hsould be removed from the signature and set of arguments that are incompatible with the python parser

[cpcloud]

@jreback @jtratner comments?

[jreback]

seems fine, any idea what factorize does?

[cpcloud]

nothing. wasn't used anywhere in parser.pyx except to be assigned as an instance variable never to be used again

[cpcloud]

looks like it was added as an option in c4d36ca and has just been floating around since then doing nothing