update docs; tag 0.2.0

release "if" demo as 0.2.0-a1

upgrade deps; update clap; tag 0.1.5

extra stack check for block; tag 0.1.4

Merge pull request #11 from calcit-lang/binary

initial support for generating binary and evaluating from binary

upgrade parser; add some tests; bump 0.1.2

try stupid nested expression; bump 0.1.1

parse CLI args