First implementation of strain workflow

Implements a suite of tools for calculating activity rate from a geodetic strain model based on the Seismic Hazard Inferred from Tectonics (SHIFT) approach of Bird & Liu (2007) and Bird et al. (2010). 

Includes:
1) General "Geodetic Strain" Class
2) Class to implement "SHIFT" - other models could be supported!
3) Reader to assign Kreemer et al (2003) regionalisation to each point in the model
4) Csv Reader and Writer for strain model (with or without seismicity rates)
5) Tests for all of the above