Improve traveltime library

[jpatton-USGS]

• I'm submitting a...

  • feature request

• What is the current behavior?
  Currently, glass3 uses a simple traveltime library that does not take into account various statistics such as TT derivatives and observability, is limited to generic phases (P rather than Pg/Pn), does not support other earth models, and uses an unneeded "warp" strategy for close in data.

• What is the motivation / use case for changing the behavior?
  To improve glass3 accuracy and performance, especially and regional and local distances