There is a huge difference between seq[uint8] and string, and that is what
people expect the type is for. People expect strings to be contain text, and
text only. People expect that a string contains only valid codes for letters,
as well as they expect that the string ends on a 0. People also know that
strings can contain multibyte characters, so indexing into a string is not
really the best idea. `seq[uint8]` is a sequence of 8 bit unsigned integers,
indexing is ok, but each component is an 8 bit integer in the range `0..255`.
`seq[byte]` can be any data, the usage has not yet been decided.
`seq[tuple[r,g,b,a: uint8]]`: now people actually expect each element in the
seq to be a pixel with 32 bit per pixel including an 8 bit alpha channel.
