- 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.

1) Allows true 'silent' running by switching off tqdm and SFThist output
2) Generalise the check old run setup to take an arbitrary set of
parameters to check (provided) they are in the saved dict. Then adds
DeltaOmega and DeltaFs check
3) Pass through the log_table and gen_tex_tables options so that one can
switch off these outputs
4) Adds create_plots to FollowUp run
5) Simple reorder to Writer parameters to group amplitude parameters

Previously changes in the number of steps required the entire setup to
be unneccerserily recalculated. This fixes this issue and attemps to
simply the logic throughout.

- Applies method to weak_signal method
- Adds methods to read/write setup files - this saves recalculating
  expensive optimial setups
- Simplifies notation and laoyout for generating setup and writing
  tables

- Add option to just update the search object in the follow-up
- Abstract loading in SFT data and check it is not already loaded before
  creating SFTCatalog
- Fix bug in plot_walkers in which the number of steps is not displaying
- Removal of unused code
- Fixes to docs

1) Moves the actual estimation to external function since it is not
contingent on using the MCMC methods etc
2) Change notation to V, Vsky and Vpe
3) Fix some table outputs (Tcoh was forcing integer)
4) Rename of names -> detector_names
5) Adds tests
6) Writes a simpler table if the sky is not searched over