make tokenize a function
Merge branch 'master' of github.com:stung/cs111timetravel
slightly change code of intoTokens
handle case for the first char in file is a newline
use token_list as node of stack instead  of stack_node
use token_node instead of token_list
Merge branch 'master' of github.com:stung/cs111timetravel

Conflicts:
	read-command.c