Spatialpy

Changes
- [287] Added simple example of spatial birth death to README and added a README to examples.

Bug Fixes
- [282] Refactored the defaults for type_id's.
- [285] Added check to raise a proper error when plotting domain types without particles.
- [286] Fixed calculation of total volume when creating 2D and 3D domains.

**Full Changelog**: https://github.com/StochSS/SpatialPy/compare/v1.0.3...v1.0.4

Changes
- improved error messages.
- [266] Added a new TimeSpan module.
- [267] Updates to the Species module.
- [268] Updates to the Parameter module.
- [272] Updates to the Model module.
- [273] Updates to the Reaction module.
- [274] Updates to examples.

Changes
- [246] Added enhanced plotting for plotting `type_id`
- [249] Added support for parameter names as a species diffusion coefficient
- [250] Added support for species names as a initial conditions species

Fixes

- Minor readme changes/fixes