Repeatable required option parses incorrectly.

[afranchuk]

From the README, I expected

exe (-l <lines>)...      repeatable( required("-l") & value("lines", ids) )

to parse exe -l 0 -l 1 -l 2 where ids would contain 0, 1, and 2. However, it tries to parse the additional -l's, and converts them to 0 values (i.e., ids contains 0, 0, 1, 0, 2).

Also, exe -l 0 1 2 is accepted (which I think should be rejected) and ids contains 0, 1, 2.