c2t: don't exhaust memory when input files aren't interleaved.
c2t: don't exhaust memory when input files aren't interleaved.

Use the lazy evaluation version, chain.from_iterable(), instead of first
extracting all items in the iterable to pass as arguments to chain().

brentp/bwa-meth,brentp/bwa-meth,brentp/bwa-meth