Some similarity metric adjustments

This makes the text similarity metric treat \r as equivalent
to \n and makes it skip whitespace immediately following a line
terminator, so line indentation will have less effect on the
difference measurement (and so \r\n will be treated as just a
single line terminator).

This also separates the text and binary hash calculators into
two separate functions instead of have more if statements inside
the loop. This should make it easier to have more differentiated
heuristics in the future if we so wish.