MODEL: Read in utf-8, only parse CSV once

Ran into `Encoding::CompatibilityError` issue trying to consume my corpus (tweets.csv) on Windows 7, but this likely affects other environments as well. 

Fix: force reading corpus file contents as utf-8.

Also a quick clean-up of the CSV flow to only parse the content once instead of double-dipping.
Merge pull request #22 from BooDoo/fix/consume-utf8

MODEL: Force utf-8, only parse CSV once