Added SpatialReference.fromESRI() method.
Added SpatialReference.validate() method. Also fixed SpatialReference.cloneGeogCS() method.
Improved documentation.
Documented maxError option for suggestedWarpOutput method.
Merge branch 'v0.3.2'

* v0.3.2:
  Documented maxError option for suggestedWarpOutput method.
  Improved documentation.
  Added SpatialReference.validate() method. Also fixed SpatialReference.cloneGeogCS() method.
  Added SpatialReference.fromESRI() method.