Pass specific words to -I flag as parameters instead of needing to use a file

[luzpaz]

Thanks to @thdot per #100 we can now use -I <file name> to ignore certain words. Each word needs to be on a separate line in the file. That is great when there is a place to save a whitelist file to so codespell can read it.

But say we were in a Buildbot environment, an automated testing framework, where we've setup codespell as a unit test... and so there isn't an easy possibility to save a whitelist file somewhere? Or another scenario, we're trying to quickly filter out a ginormous list of false positives from a codespell result, one needs to open their favorite editor and add each word on a separate line and link said file. It's not the most efficient.

It would be then useful to then have the the ability to pass the whitelisted words sequentially ex. codespell -I 'nto,ans,pres,ot,amin'
Thoughts?