Apsg

* Ellipsoid repr bugfix

Bugfix release
* slip and dilatation tendency methods added to stress
* proj alias of project for FeatureSet added

* added title_kws argument for plotting routines

* sigma estimate contour fix

APSG offers convenient pandas integration via pandas accessors.

See documentation and Pandas interface tutorial for further details.

* StereoNet tensor method added
* Cluster class renamed to ClusterSet

* lambda properties of tensors renamed to S
* cursor coordinates in stereonet show lin and fol