Use sampleSize when appropriate.
Add section comment for initial batch of generally useful functions.
Add iterateMaybe, generalized from bestRefinements.
Make section comment on feature construction functions more accurate.
Merge branch 'fix-features-comment'

* fix-features-comment:
  Make section comment on feature construction functions more accurate.
Make comment on main more accurate; no longer a small sample.
Make comment on main more accurate; emitting model now, not just testing.

* commit '3c48d17':
  Generate test-weights from analyze.hs
Merge branch 'fix-main-comment'

* fix-main-comment:
  Make comment on main more accurate; no longer a small sample.
Specify list of all words on command line.
Rename logfreq set files to clarify the order of comparison.
Don't produce or use logfreq set files.
Compute logfreq table from freq table.
Specify logfreq file on command line of analyze.hs
Add parsing of word-float tables.
Allow user of bestRefinements to specify quality function.
Add computation of normal distribution pdfs.
Add ClassWeight type and implement the size-based classes in terms of it.
Compute weights by fitting a lognormal distn to word frequencies.
Use Text instead of String when possible.
Compute meanAndVar in constant space.

This is a typical laziness pitfall; here, the foldl' computing
the accumulator strictly means only that the tuple constructor is
evaluated, leaving the contents of the tuple as thunks, which then
nest as deep as the list.  The new version is strict in each of the
accumulators in the tuple.