NERSC job submission

[johnkit]

Adds new capability to submit jobs on NERSC (Cori machine) to crop raster datasets.

• Extends gaia.connect() to accept NEWT session id for authentication
• Adds gaia.submit_crop() to submit jobs to Cori
• Adds nersc_login,ipynb and job_submit.ipynb notebooks to docs/examples folder
• Adds geolib.py file to provide "geolib" alias
• Updates GirderInterface.lookup_url() to accept cumulus job id as input
• Adds GirderInterface.ls() to list files in girder folder
• Updates gaia.create() to accept optional bounds argument (needed for data from ESS-DIVE and cumulus asset stores)

[coveralls]

Coverage decreased (-6.2%) to 35.749% when pulling 4684d98940c337dd4144f0ce49fd831222c1517c on johnkit:job-submit into cabd47430dbaeccb207760e809610a5df44e1319 on OpenDataAnalytics:master.