No longer saves the emcee sampler itself to the pickle. This was done in
response to a bug encountered by David Keitel in which while dumping the
pickle an error was raised. Fixes #1

Requirement is matplotlib>=1.4 in order to use the style package. Make the
default context ggplot (available in 1.4) and add an error message to
help the user when they have selected one which does not exist.

Adds proper unit support by default, and options ot customise through
the dictionaries

- Adds latex prior table writer (not found to be useful)
- Add special case of 0 to texify_float
- Expose texify_float in core
- Fix confusing argument order in GridSearch

- Fixes undefined theta_values -> theta (missed as Ng > 1 isn't tested)
- Import from core rathern than explicitly
- Various PEP8 fixes

- Fixes missing sqrt in the convergence test
- fixes error in periord
- prevents plotting between burn and prod
- allow user to specify upper limit
- refactor code

This was mistakenly added during a testing phase - removed since it is
not used.

- restructures the method into several different functions.
- implements stopping if convergence is met a prespecified number of times
- adds documentation
- will plot the convgerence on the RH axis of the walkers plots

Convergence testing based on the Rubin-Gelman statistic is implemented
via `setup_convergence_test`. This does not truncate the search yet, but
simply adds a trace to the walkers plots for testing

- Addresses incorrecelt named attributes and prevents error if
  sftfilepath is not specified

Also adds thetas_at_ref data to the Writer object

Transforms the single pyfstat.py into a python module splitting the
relevant code into separate sub-files in pyfstat. This should result in
improved readability.

1) Update README installation instructions
2) Put all set_up code into seperate named functions
3) Remove underhanded mpl backend setter

Use N=1000 for the recoveries and N=10000 for the test in noise

Issues:
1) If tstart and duration where not explicity searched over, a loop
condition would quickly send the duration to infinity
2) Fixed half norm definition

Rather than starting with the fully-coherent Vsize, this now starts with
the input Nseg0 (i.e. from the SC search). and works back to Nseg=1.
The user is then left to check the V0 value and whether the search is
appropriate or not. Applies the idea to the follow-up example.