Geocat-viz

**Release Notes:**

Updated functionality:
- Existing functionality reorganized

New functionality:
- implements pre-commit hooks
- creates a place for future documentation on RTD
- restructures the repo for the purpose of adding plotting functionality that exceeds convenience/utility functions
- adds a conda environment specific to -viz development
- updates to README and INSTALLATION files to reflect new functionality and structure

Release Notes:
- Updated functionality:
1. **add_major_minor_ticks** (https://github.com/NCAR/geocat-viz/pull/12)

- Added functionality:
1. **set_vector_density** (https://github.com/NCAR/geocat-viz/pull/10)
2. **set_map_boundary** (https://github.com/NCAR/geocat-viz/pull/11)
3. **plotCLabels** (https://github.com/NCAR/geocat-viz/pull/16)
4. **plotELabels** (https://github.com/NCAR/geocat-viz/pull/16)
5. **findLocalExtrema** (https://github.com/NCAR/geocat-viz/pull/17)

- Removed functions (which were previously deprecated):
1. **nclize_axis**
2. **make_byr_cmap**