Offset of scalars, fixed and terminated arrays.

See #63.
Revert `t/cover`.

I had narrowed coverage to just the offsetOf function since a full
coverage report takes longer than a minute. Reverting `t/cover` to full
coverage before I forget. I didn't mean to check this in.

See #63.
`offsetsOf` for specified terminators.

See #63.
Merge branch `master` into `offset-of`.
`offsetOf` length encoded array.

See #63.
Merge branch `master` into `offset-of`.
`offsetsOf` single positional byte.

See #63.
Reuse named loop in `offsetsOf`.

See #63.
`offsetsOf` a positional array.

See #63.
`offsetsOf` positional terminated array.
`offsetsOf` positional length encoded arrays.

See #63.
Move subroutines specific to `offsetsOf` into it.

See #63.
Create an `Array` in `offsetsOf` when not named.

See #63.
Cull dead code.

See #63.
Dedent.

See #63.
Subsequent after terminated array in `offsetsOf`.

Test that `offsetsOf` will continue to operate on fields after a
terminated array.

See #63.
Remove `outgoingIndex` from `offsetsOf`.

See #63.
Remove dead conditional.

See #63.
Dedent.

See #63.
Notes on positional callbacks.

I'm going to reimplement Packet to accept object callbacks, fake
positional callbacks, which means that it will be easier to implement
logic like `offsetsOf`. I'm getting stuck on bit packing, seeing how it
would be so much easier if it was objects only.

Closes #63.