Add firebase synching between three towns

Towns keep own accounts of the numbers of balls they send
to each town, and read the values from the other towns
to add their own balls.
Solve network flow and direct energy using Edmunds-Karp

Each town checks the production and needs of each other town, and
independently solves the network flow algorithm (which will return
the same for each town) to decide where to send energy.
Set capacity between towns to be narrowest pipe btwn them
Merge branch 'refs/heads/master' into gh-pages