Optimizations for multi-threading #111
Description
It would be great to have a mode that needs to lock the reader for as little time as possible when using multithreaded IO. In particular when parsing plain fasta files, that means it's probably better to just search for the next > character and copy everything up to that point into a new Vec owned by a thread. Then the searching for newlines and stripping them could happen in the thread itself, rather than on a SequenceRecord<'_> which (via the lifetime) holds a lock on the main Reader.