tools/png: Begin work on node.js port

Addresses #12.
tools/png: Complete port to node.js

Addresses #12.
tools/png: Add some extra function documentation

Addresses #12.
tools/png: Export Configuration to env namespace

Addresses #12.
tools/png: Use pngrc to set populated chances

Addresses #12.
tools/png: Import real populated values

Addresses #12.
tools/png: Parse command line options correctly

Addresses #12.
tools/png: Throw an error on unrecognised file format

Addresses #12.
log: Add notes for Saturday
tools/png: Add --format argument

Addresses #12.
tools/png: Add --help|-h usage information

Addresses #12.