Fixes, tests and documentation

Since February I spent time learning about revealing pairs via the paper of Salazar-Díaz. Consequently, some experimental functions were added to the package---in particular methods to see when a tree pair is revealing, and a method which calls pdflatex to render the automorphism as a tree pair.

The remainder of the work was on tests, fixes and documentation. The implementation of the conjugacy test was consistent with Hossain's ConjugacyF when working in the group F. I added a Jupyter notebook to give a nice illustration of how we can use the package.