Code to spit out problem variants added.

When doing an executemany insert, we lose the ability to
find out exactly which variant is causing an error. This
goes through the variants of an executemany insert
one by one until variant causing the exception is found.
Merge with master.
Merge pull request #114 from roryk/master

Easier problem variant identification
Merge pull request #115 from chapmanb/master

Fix for issue #113 + documentation + small installer fixes
update requirements to last commit.
pfamA domains annotation provenance
Merge pull request #116 from udp3f/master

domains annotation provenance
Provide a variant annotation to identify context specific sequencing errors (CSEs): useful to identify potential false negative calls.