HydroShare on Jupyter 0.1.5

• Support for Safari is added (see issue #98 for background).
• A minor frontend server root path issue is resolved (see pr #99's summary for details)
• Both frontend and backend are bumped to 0.1.5 (resolves #97)

Additions

• Backend:
  • ServerRootHandler added. Endpoint responds with expanded absolute directory path location of where JupyterHub session was started. Endpoint path is: /syncApi/root_directory/.

Changes

• Frontend:
  • Location of serverRoot is now retrieved from backend ServerRootHandler at /syncApi/root_directory/
  • No longer use Array.at to index array. Resolves #98