Pyyeti

This version builds on the previous version (0.99.5) to fix bugs and enhance the Nastran op2 reader tools. Also added more op2 reader tests.

This update is all about enhancing and fixing a bug in the Nastran tools. The bug was that pyYeti did not properly handle upstream superelements that did not connect all 6 DOF for all boundary grids. This can happen for superelements brought in via EXTSEOUT.

Also enhanced the PARAM,POST,-1 op2 file reader (the pyyeti.nastran.op2.rdpostop2 function) to return more information organized by superelement.

Bug fix for the op2 reader (now can handle more than 32 superelements).
Update the n2p.find_xyz_triples routine to be more robust and added the "tol" parameter.
Update the README.md file to update the install notes

Minor update; primarily made the matplotlib import in setup.py optional by using try/except.
Also improved testing for the new "asm2uset" routine.

Primarily minor documentation updates and bug fixes.
Enhanced the nastran.bulk.rdseconct routine to accept more card formats.

- update uset usage in cb.cbcheck and cb.mk_net_drms (can include non bset DOF)
- attempt to prevent datacursor.DataCursor._setup_annotations() (scatter) from resetting axes limits