Add automated tests for common use cases

[gaurav]

Look into Vue.js' testing support to ensure that a few common user cases are tested:

• An example file can be opened and the phyloreferences and phylogenies examined.
  • Additionally, the phyloreferences can be navigated to and edited. Editing the phyloreference causes the "you have edited this document" warning to appear, and undoing the change causes this error message to disappear (see Reactivate ModifiedCard to warn users about exporting the Phyx file #166).
  • Additionally, the phyloreferences can be resolved using JPhyloRef, and the results of the resolution visible in both the Phyloref View and on the individual Phyloreference views.
• A new phyloreference can be created. If an invalid phyloreference is entered (e.g. without an internal specifier), a warning appears, which disappears when the problem is corrected.
• A new phylogeny can be created. If an invalid Newick string is entered, an error message appears, which disappears when the Newick string is corrected.

See #85 (comment) for suggestions on using Selenium to run these tests.