Fixed the exception to ImportError specifically. - Realised that the exception was too generic and allowed passing   different kinds of error. This exception is only meant for the failure of importing `Basemap`. Right now it will leave aside `visualization` functions on any import failure. This could be improved. 	modified:   opsimsummary/__init__.py
Fixed the exception to ImportError specifically.
- Realised that the exception was too generic and allowed passing
  different kinds of error. This exception is only meant for the failure
of importing `Basemap`. Right now it will leave aside `visualization`
functions on any import failure. This could be improved.
	modified:   opsimsummary/__init__.py

rbiswas4/simlib