v3.0.0

As per semantic versioning guidelines, this will be called 3.0.0 since it contains a moderate backwards compatibility break.

Removed pyradox.struct.List as per #2.

key = { value0 value1 value2 }

is syntactic sugar for

key = value0 key = value1 key = value2

Use the findAll(key) method to iterate over all values matching a key.

Some other improvements to Tree methods.