Histomicstk

Fix dependencies.

More annotation workflow features.

Add new functionality for using HistomicsTK as a python package to interact with the DSA annotations to:
1- Create mask from annotations on the DSA server.
2- Extract annotations from mask and post them to HistomicsTK server for display.
3- Handle complex polygon mergers (eg tiled segmentation results).

Also,
1- Update installation instructions
2- Improve documentation

- Changes base image from ubuntu:14.04 to dsarchive/base_docker_image that includes miniconda, python wrapper ITK, and openslide on ubuntu14.04. With this change ITK will be available for use within HistomicsTK when run within the dasrchive/histomicstk docker image.
- Adds examples using jupyter notebooks
- Sets up the infrastructure to add tests using data stored on data.kitware.com
- Adds front-end code to display annotations

This release fixes a few bugs in the generation of annotation files by the Nuclei Segmentation CLI.