Tweak default dot radius one final time

After testing, a dot radius of 12 seems to be a good default.
New approach to create new font: copy, then change

Instead of creating a new font from scratch, we'll copy the TTF file
provided and use that as a basis for the font creation process. This
will mean that all sorts of things will be copied over, like font name,
copyright information, etc., which may need to be modified. But it's the
best way of ensuring that glyph anchor points, lookup subtables, and so
on are copied into the new font.
Add installation instructions to README
Start looking for p2t.so from source dir, not cwd

The starting point when hunting for the p2t.so file should be the
location of the Python script, not the current working directory.
Add TODO section to readme
Added future-improvement ideas to README
Simplify project directory structure

All Python files now live in the root of the project, for simplicity of
telling other people "check this repo out and run it".
Give hint to users who run wrong file