Fix bug in pretty printing of perplexity results.
Initial attempt to speed via diagonalization of prior covariance the performance of CTM
Tidy up the code for the real-world unit tests, and use same scaling code throughout
Rename "fastButInaccurate" to the more sensible sounding "useDiagonalPriorCov"
Rename "tier" variable to "itr" to avoid clash with built-in function name
Get main script working - still incomplete.