v0.12.1

Thermochron v0.12.1

Diff since v0.12.0

• Randomize initial proposal subject to max reheating rate
• Add optional alpha injection correction, if matrix U-Th-Sm is specified
• Make GenericHe alpha stopping distances mineral-specific by scaling Farley et al. 1996 decay-specific distances by relative stopping power as calculated from Ketcham et al. 2011 average distances
• Update @info statements about chronometers under inversion in MCMC functions