Cleanup/reorganization

[rjtayl]

We've made the major changes to how spec_sims was organized that I wanted. There may be some cleanup and improvements we could still make but I believe all the changes that would have made parallel development and merges difficult have been completed.

Major changes:

• We now use a pyproject.toml to package everything because setup.py is deprecated for our use case. This caused the source files to be moved into a src folder. Also simplified installation, see new readme.
• Broke simulation_blocks into separate files
• better variable sharing between classes --one constants.py variable for physics and math constants --one rng shared between all simulation blocks
• cleaned up gitignore and removed personal and runtime files

[buzinsky]

Looks good to me - produces the same results as before I think more classes (e.g. Beta, or Event) to collect these variables (center_theta, z_max, radius, energy...) would be nicer than passing many arguments I also see this as lower priority. We have the power to deal with merge conflicts, should they happen

[rjtayl]

Yeah I agree we should eventually make those classes, after the more urgent features we've discussed.