New Integration class

- Integration class (handles logy/logt/scaling)
- Added new example equilibrium, with test
- Fixed minor bug in cvode_direct
- CHEMREAC_SOLVER_KWARGS picked up by run()
- New analysis convenience function: solver_linear_error_from_integration
- New plotting function: plot_solver_linear_error
- New plotting function: plot_solver_linear_excess_error
v0.2.2 release

- PEP8 fixes
- Fixes #12
- Documentation improvements
- tweaks for examples
- Use ndarray instead of memory view in wrapper.
- sdist and Docker file to test sdist
- Better test coverage.
- Correct scaling.
Merge pull request #28 from bjodah/scaling

New Integration class supporting scalnig. v0.2.2 release.