add support for noreply

the memcache protocol defines a 'noreply' optional parameter, which
instructs the server to not send a reply. In heavy usage environments
this can lead to significant performance improvements.
add support for pluggable compressor/decompressor

Add support for pluggable compressors.

zlib is a fine choice for a default compressor, but in some environments
alternatives (lz4/lzf/snappy) that offer differet tradeoffs for
size/time, may be preferred.
CAS supports noreply too
fix delete to actually return nonzero on failure

currently, delete will return success on NOT_FOUND, due to NOT_FOUND
being in the expect list. This seems like a bug, given the method
description of "@return: Nonzero on success". Remove NOT_FOUND from
delete expect list.
Merge branch 'fix-delete'
Merge branch 'support-alternate-compression'
add lots of tests