Update readme

Note: for some reason `dub run` and `dub build` throw linker errors,
however compiling with dmd does not. Please run with
`dmd -of=stf **.d && ./stf` in the mean time.
Write lexer
Write first design draft
Clean out project for rewrite
Finish parser

Parser now moved from model.d to parser.d. Created new interpreter.d and
laid out base of struct for it.
Start project

Add gitignore, created skeleton main program and hello world test file.
Initial commit

Add GPL3 licence, short readme, and dub.sdl file.