Use longest match when parsing a `sequence-set'

For example, "15:16" sequence set was parsed as "15", and
`response_data` parser would succeed on "* VANISHED 15\r\n", but would
fail on a valid "* VANISHED 15:16\r\n" response.
Merge pull request #6 from ALPHA-60/fix-sequence-set-grammar

Use longest match when parsing a `sequence-set'