Make blockchain() and boundchain() in node methods (rather than functions).
add emacs backup files to .gitignore.
assert that get() method returns either the empty string (EOF) or a single
character.
change node::boundchain() to return a list of declarations, rather than a list
of blocks.
remove once-used variable.
Prettify token::__str__() output.
Fix handling of number literals starting with 0: int(x, 0) doesn't accept them.
add rep: read-eval-(no print yet) loop.