add wrapper example
several small improvements

- fix column alignment when highlighting
- use [7mto reverse video[0m
- start validating input makes sense
add example script w/ escape color seqs
validate input and simplify processing
tweak when redefinition of scripts is done
wrap SCRIPT_DESC w/ quotes
allow exit in command strings

This allows input like "1 2 exit".
slight wording in README
CUSTOM_ENV -> CUSTOM_ENV_SH
SCRIPT_DESC -> SCRIPT_NAME
adds extended help; closes #1
pad menu items; closes #2