Fix Makefile dependencies
Lex strings, fix shift/reduce, parse multiple statements

Singly and doubly quoted strings both work properly now. Comments still
need to be implemented.

Fixed 4 shift reduce conflicts. 2 involved conflicts with unary operators
and postfix operators. 2 involved conflicts between additive and
multiplicative operators. The fix was to specify the precedence of the
unary operators and additive operators as below the postfix and
multiplicative operators respectively. There is still a shift/reduce
related to try, catch, finally, but I know how to resolve it.

Also added the ability to parse multiply statements, since this was
something I'd neglected earlier.
Implement comments
Parse empty file correctly