Improved build instructions for fresh clone of repository
fixed run_websocket way of running websocket app
Fix proper error reporting
Adding documentation on how to build submodules
Added pyzmq as the dependency
Merge remote-tracking branch 'github/master' into fix/websocket-deploy

* github/master: (34 commits)
  Properly fix Facebook group fetching
  Adding documentation on how to build submodules
  Improved build instructions for fresh clone of repository
  Fix the name of an Image field to match the model
  Upgrade Flask-Admin to bump minor version
  Remove Celery from requirements
  Return 404 if tile not found
  Fix for loading ptif files with correct tile_size
  Remove 'Image.extents' field
  Clean some trailing whitespace
  Remove commented stack PDB debugging statements
  Fix Python style issues in glviewer
  Don't provide a default value for image dimensions
  Save tile size with changed name
  No need to delet if session not found
  A sesssion's 'hideAnnotations' field should be a bool
  Use absolute paths for tiles in session editor
  Don't use a leading dot in URLs
  Create all model mutable default values using a callable
  Make 'Image.dimensions' a required field
  ...

Conflicts:
	requirements.txt
Merge branch 'fix/websocket-deploy'

* fix/websocket-deploy:
  Added pyzmq as the dependency
  Adding documentation on how to build submodules
  Fix proper error reporting
  fixed run_websocket way of running websocket app
  Improved build instructions for fresh clone of repository
Disable validation of Session Annotations until all code supports it

This was causing failures in "/webgl-viewer/stack-save".
Merge branch 'session_annotation_validation'

* session_annotation_validation:
  Disable validation of Session Annotations until all code supports it
Better stack interpolation, and correcting errors
Merge branch 'stack-annotation'

* stack-annotation:
  Better stack interpolation, and correcting errors
Add new authorization functionality with Flask-Principle
Merge branch 'authorization'

* authorization:
  Add new authorization functionality with Flask-Principle
Object Ids instead of strings
Merge branch 'Stack-fix'

* Stack-fix:
  Object Ids instead of strings
Fix a transient bug in authorization
Merge branch 'authorization_fix'

* authorization_fix:
  Fix a transient bug in authorization