Make FeatureSpec easy to instantiate

Have setters return a ref to this so they can be chained together.
Error in how tweets were being read in - confused the time-dff column for the messsage and ignored the message itself
Errors in unit test

Forgot to write out files with newlines. Made tabs explicit. Forgot to
updated counter in testAccount (to move onto the next expected value).
Also flexhed out test on feature-extraction.
Many improvements in feature extraction

Better retweet detection (using account to author match)
Better recovery from corrupted lines in the files.
Better logging of progress.
Secretly add an interface to help unit testing (can pass a file instead
of a directory if the file is < 1min old)