[WIP] Add touch to the ASCII protocol.

Touch is defined for the ASCII memcached protocol, but not implemented in
spymemcached.  This commit adds the missing touch functionality.

The ant test suite as described in README.markdown does not pass out of the
box (without this commit). Here is a log of the test:

https://gist.github.com/mweiden/19980a35c48a69654ea1

Details of my local setup:

Mac OS X 10.8.3
Memcached 1.4.15
Spymemcached 2.8.12

Tests that fail as reported by ant:

[junit] Test net.spy.memcached.AsciiClientTest FAILED (timeout)
[junit] Test net.spy.memcached.AsciiIPV6ClientTest FAILED (timeout)
[junit] Test net.spy.memcached.BinaryClientTest FAILED (timeout)
[junit] Test net.spy.memcached.BinaryIPV6ClientTest FAILED (timeout)
[junit] Test net.spy.memcached.QueueOverflowTest FAILED
[junit] Test net.spy.memcached.TapTest FAILED

With the new commit added, the touch functionality does work when tested by hand. These tests still fail.

@daschl @dustin @mikewied: Please advise me on how to fix these issues and let me know of any project conventions the code should conform to. Was there a specific reason that this functionality has not yet been implemented?