fix cvc4 options
improve readme
some comments
Update lexer tests with case sensitivity
positioned tokens
stricter interface for s-expr lexer
Lexer is an iterator of tokens
Parser is an Iterator of SExpr, and tests are adapted
clean up comments
add a test for pretty printer
testing command parser
testing response parser
fix a bug with singleton tokens and positions
add a few sections to the README
fix typo
todo
Support for define-sort command
testing more commands
no more sbool unapply
complete parsing of most SMTLIB commands, with tests