The first release of PySolid.

• add/modify solid.for from Dennis Milbert for solid Earth tides (SET) calculation following the 2003 IERS Conventions by @yunjunz @sssangha.
• add two modes at Python level to call Fortran code for SET calculation with API usage and examples by @yunjunz:
  • point for 1D tides time-series at a specific point for a given time period
  • grid for 2D tides matrix at a specific time for a given spatial grid
• add setup.py and pre-compiled C extensions to support pip install git+https://github.com/insarlab/PySolid.git by @yunjunz.