While investigating basho/webmachine#186 it was noted that a small but
non-zero percentage of clients embed whitespace in Range headers. It
appears this is valid:
byte-range-set = 1#( byte-range-spec | suffix-byte-range-spec )
...separated by one or more commas (",") and OPTIONAL linear
white space (LWS)...
...null elements are allowed, but do not contribute to the count
of elements present. That is, "(element), , (element) " is permitted,
but counts as only two elements...