Merge branch 'develop'
Merge branch 'develop'

Marks version 0.2.0 of DIQS/DIMS. Much improved memory usage, and preparation for slimming
down memdb quite a bit to simplify the database. Plans are to remove removeImage() method,
allowing the removal of internal tracking of image IDs to locations in the DcRes array.

The reason for this is the removeImage() method wasn't used at all except in unittests, and generally
reloading the MemDb entirely led to a more cache friendly memory layout.

The next plan is to separate LevelDb and MemDb further, so a leveldb can build its on-disk database
without having to also insert its images into a MemDb. Perhaps it'd be better to provide
a method such as genMemDb to PersisteDbs, which return a generated MemDb from the images
they're processed and persisted?
updated readme
add travis build badges