changed random seed to avoid multi-modal posteriors.  Added comments to tutorial so user can understand each step

- If no saved data exists when loading, a valueerror is now raises. This
  catched that exception to work as expected.

- Adds a filename option for direct loading
- Raise an error if no information given

Moritz Huebner: Made sampler.result a property and moved some of the stuff that happens in run_sampler in there.

# Conflicts:
#	tupak/__init__.py

If DISPLAY environ not found, then default to the Agg matplotlib
backend. Useful for running on clusters etc.

Moritz Huebner: reintroduced kwargs property/setter, is probably better because that behaviour is getting inherited

Adds a basic command line interface

Closes #68

See merge request Monash/tupak!40

Adds a basic command line interface

Closes #68

See merge request Monash/tupak!40

Closes #68 by giving a simple interface to set the log-level (unless set
at the script level) and whether or not to use cached data.

Adding cached data check

Closes #64

See merge request Monash/tupak!39

- If the sampler kwargs are the same
- If the search parameter keys are the same

MISSING: check the priors. This requires a more detailed look into how
to compare our prior distribtions.