- Resolve unspecified values on instantiation
- Add a check for masking key length
- Smarter resolution for masking_key and mask values. Do the right thing unless told not to.
We don't really need this any more. The interface is much less error prone
because bit flags are no longer integers, we have a range check on opcode on
header instantiation, and we've deferred length code calculation and so forth
into the byte render methods.
- Separate out FrameHeader. We need to deal with this separately in many circumstances.
- Simpler equality scheme.
- Bits are now specified by truthiness - we don't care about the integer value.
This means lots of validation is not needed any more.
