ENH: changed citation references to bibtex, fixing typos as seen

ENH: added bibliography page `zreferences.rst`and added it to `index.rst`

ENH: added bibtex functionality within conf.py, converted citations as `refs.bib

DOC: Add script that corresponds to the new tutorial_get_rainfall to examples directory.

DOC: Revising three outdated tutorials.

Corresponding to Issue #45, this commit revises or replaces three outdated tutorials:
tutorial_conversion.rst, tutorial_accumulation.rst, and tutorial_clutter_correction.rst.

The latter is removed without replacement - volunteeres are invited to replace it...

FIX: fixed wrong path in example

FIX: added unzipping/removing of zipped radar data to example file

FIX: fixed some docstrings and type on docs

FIX: fixed docstrings and `vis` autodoc items

FIX: fixed some docstrings and removed/changed calls to deprecated functions

FIX: exchanged deprecated plot function

FIX: removed all deprecated functions and examples

Automated merge

Added tag v0.2.0 for changeset d90b6bceb268

MIN: Set version from 0_1_1 to 0_2_0.

This is based on our discussion in issues #41 and #42.

DOC: Expose read_generic_netcdf in the API documentation.

DOC: Revised NetCDF section in supported formats tutorial in order to include read_generic_netcdf.

MIN: Fixed a docstring typo.

MIN: Added license to example header.

ENH: Adding a generic reader for NetCDF files to the io module (read_generic_netcdf).

This reader is based on Kai Muehlbauer's suggestion from Issue #36
(https://bitbucket.org/wradlib/wradlib/issue/36/wradlib-should-support-cfradial)
with a few minor modifications....