Climbing Ratings 1.2.0

Changes since 1.1.0:

• Switched to using log-normally distributed priors for the "gamma" ratings, instead of gamma-distributed priors.
• In the routes.csv input to 02-run_estimation.py, rename grade to gamma. This means inputs generated with previous code will need need to be regenerated (or manually fixed).
• Drop climbers with no "non-clean" ascents in pre-processing.
• Stop classifying "tick" as clean.
• Some regression tests for top-level scripts.