Readgssi

- moved plotting routines to new module `plot.py`
- moved translations to new module `translate.py`
- moved gps reading to new module `gps.py`
- moved geophysical and GSSI constants to new module `constants.py`
- moved stacking algorithm to `filtering.py`
- significantly improved layout of main processing function `readgssi.readgssi()`
- script flow is *so much more natural now*
- made way for future additions like interactive picking
- csv output improvements
- added the ability to filter prior to csv export (duh?)
- added the ability to export multiple csv files when more than one radar channel is present
- improved histogram plotting
- improved array handling when passing to functions
- changed the way files are named if no output file is passed (the Seth Campbell Honorary Naming Scheme)

- moved filtering routines to new module `filtering.py`
- added a way to call `readgssi.__version__`
- moved some config stuff to `config.py`
- bitwise datetime read works properly now!! this was a longstanding bug that took me forever to figure out. the bit structure was not at all intuitive and the script kind of ends up using brute force to decode them to datetime objects, but it works. dates and times of file creation and modification should now match those in RADAN.
- changed to verbose by default and quiet if `-q` / `--quiet` flag is set
- changed print statement to output date and timestamp (helpful for tracking date and time of things when, for example, processing a whole survey data folder full of radar files)

- added ability to install via PyPI
- setuptools integrated command line script creation (i.e. `readgssi` instead of `python readgssi.py`)
- broke out several routines into individual functions

- now define time zero point manually (time zero is when the direct wave passes the receiver. previously, i used an unreliable calculation using header values to determine the time zero point)
- in the future, i will add a signal processing algorithm to detect the time zero point automatically
- added bandpass filter (requires [obspy](https://obspy.org/))
- significantly optimized background removal and dewow algorithms
- added example code and plots
- fixed a bug that caused both plots of dual-channel radar files to be written out to one file
- fixed a bug that caused manually-created output file names to be ignored when plotting
- added basic background removal and dewow capability ([5](https://github.com/iannesbitt/readgssi/pull/5) from [fxsimon](https://github.com/fxsimon))
- added support for the D50800/D50300 antenna
- added plotting support for dual-channel radar devices
- merged [3](https://github.com/iannesbitt/readgssi/pull/3) from [fxsimon](https://github.com/fxsimon) which fixed a bug that caused multi-channel file traces to be read in a 121212 sequence instead of 111222
- updated the workings of the plotting algorithm's colormap
- changed the way files are saved (bug in 0.0.5 mangled some filenames)
- added the ability to specify colormap and whether to draw a colorbar and a histogram
- added an automatic figsize option (leaves figsize up to Matplotlib)
- added ability to apply gain
- fixed bug that caused gain to be applied incorrectly
- script now tries to automatically calculate timezero using (nsamp\*range)/position