New tip branch

This will fail tests for a while.
Implements:
- a custom reader
- an identifier type
- a PronomIdentifier
working on siegreader
apply travis fix from master
working on siegreader
set priorities on bytematcher
separating buffer from reader in siegreader package
read methods directly on buffer
siegreader almost done
siegreader fixes
slouching towards bethlehem

a lot still needs fixing
must slice must return a byte slice!
tests are passing again!
tidying up API
pronom tests work too now
works again, but slower!
speed

also fmt/61 and fmt/62 are identical test. So removed one.
further optimisations
Merge branch 'v2'