Replace single insert state with insert states for each of A, C, G, T

[psathyrella]

Erick's idea -- this allows us to take into account the fact that two clonal seqs have the same inserts

As part of this, should update/check get_emission_prob() in hmmwriter.py

[psathyrella]

7913843

Turns out it helps! woot.

before:

after:

NOTE binning is confusing (the bin width is different for the different colored histograms). All are normalized to number of entries though.