Overdue update for master

In late September or early October, a few of us realized the master branch was far away from the working develop branch. This release re-syncs the two branches and introduces a few changes in how davitpy code is imported and data are read. Also of note is the change to installation and local configurations and environment variables. It is recommended that the old code be tucked away in a closet (or removed) and the new master used here. While this release does not include a few features, enhancements, and other bugfixes, we expect to have another release branch in a few weeks and another master release just before Fall AGU.

Here is a summary of changes since the 0.3 release:

1. Pythonic data pointers for radDataRead and sdDataRead
2. Generalized file fetching and
3. Removal of mastermake (everything handled in setup.py now)
4. Refactoring of codebase directory structure: pydarn, utils, gme, and models are now inside a davitpy directory. Consequently, installing DaViT-py now installs a davitpy package instead of separate packages for pydarn, utils, gme, and models.
5. Removal of environment variables for configuring davitpy (handled by a davitpy.rcParam dictionary now). Custom configurations are read from a davitpyrc file that can be placed in the user's home directory.
6. Various bugfixes.
7. Added the ability to plot rawacf and iqdat files.
8. Added ability to plot the backward FOV of radars
9. Polished the coordinate conversion code and unified it under the utils submodule

Please report any bugs by filing a new issue at https://github.com/vtsuperdarn/davitpy/