Bug	23893. Switch filename check from str to basestring.

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 128473]
Use Bullard's lazy caching scheme to back zmw.readScore and zmw.productivity

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 128539]
Add a symmetric "put" method for GFF3Record

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/lib/python/pbcore/": change = 128713]