added function generate_submodel
updated example
Added a cool example to generate submodels from.
some notes about graph drawing packages
Update README.md
Formulas are now encoded as tuples.
Merge branch 'basic_modal_logic' of github.com:winobes/modal-logic into basic_modal_logic
Add smallest filtration.
Changed Language to mediate between symbols (characters) and their meanings.
Add largest filtration.
Use 'diamond' instead of '\u25c7'.
Update README.md
Update README.md
generating random propositional formulas
cleaned up the inheritance of Model from Frame
added a GUI
draw routine
changed the handling of unary operators
Remove debug prints.
Add initial support for normal forms and truth tables.