v0.3.0

Breaking changes

• Change the bounds checking behaviour of the find* functions to match those of
  Vector. In particular, previously, findnext(pred, mem, -5) would be
  equivalent to searching from index 1, and similarly, findprev(pred, mem, lastindex(mem) + 10) would be equialent to searching from lastindex(mem).
  Now, searching from an index before the first valid index throws a BoundsError.
  Findfirst searching from i > lastindex(mem), and findlast searching from
  i < 1 will still simply return nothing, just like searching vectors.

Other changes

• Add optimised versions of findprev and findlast, searching bytes
• Add optimised version of find*(iszero, bytes) methods
• Add optimised generic find* methods
• Add functions split_first, split_last, split_at and split_unaligned
• Add a more correct implementation of Base.mightalias for memory views and
  some types of arrays