Pyyeti

This update is primarily about testing updates:
- switched from nose to pytest
- cleaned up some tests
- reduced useless warning messages during tests

Updated the README file.

There were no significant pyYeti changes from a user's perspective.

This is a bug fix and deprecation fix release primarily:

- add "RVAX" datablock to output of nastran.bulk.wtextseout
- also added the `namelist` argument for more user control of op4 output
- began updating build/install/test codes to more recent standards
- added failure example for the nastran.n2p.find_xyz_triples routine

Primarily an update to the datacursor. The interface for external use has been enhanced and cleaned up. It now also handles scatter plots and 3D plots much better. Unfortunately, some of the updates are not backward compatible. For example, the label formatting provided by the "form1" and "form2" functions has been updated to a single function: "mk_label". See the documentation for more information.

Minor update. The primary update was to rewrite how the over-damped ode.SolveUnc integrator coefficients are computed. Previously, high damping could cause an overflow issue because of the use of cosh & sinh functions.

A small update, primarily to cla.DR_Def.add:
- update handling of "drfunc" checks and improve error messages
- change some SRS defaults (srsopts and srsconv)

Minor update:

- add scale_by_Q_only to srs.srs_frf
- update cla tools DR_Def and DR_Results to be able to accommodate more flexible SRS options