Increment MINOR version number

Increment MINOR version number, to give complete version as 0.1.0.dev.
Correct equation-sorting algorithm

Correct equation-sorting algorithm to run as intended:

* Identify lowest PageRank value
* Identify nodes with that PageRank value (there may be more than one)
* Sort the candidate nodes alphabetically and take the first node from
  that list

Subsequent improvements should consider how to incorporate supplementary
information about the candidate nodes e.g. in-degree and/or PageRank.

Update test function to store new expected output.