text: Title: UserWarning thrown when importing hypertools in jupyter notebook
  Body: When importing hypertools in a jupyter notebook (`import hypertools as hyp`), the following warning is thrown:
  
  ```
  /opt/conda/lib/python3.6/site-packages/matplotlib/__init__.py:1405: UserWarning: 
  This call to matplotlib.use() has no effect because the backend has already
  been chosen; matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
  or matplotlib.backends is imported for the first time.
  
    warnings.warn(_use_error_msg)
  ```
  
  Proposed fix: suppress this warning within hypertools (more info [here](https://docs.python.org/2/library/warnings.html))