upgrade Makefile.PL
list all the dependencies
new target to install the cmdline utilities

also allow to override the '/usr/local/' prefix by defining the
SHARDCACHE_INSTALL_PREFIX environment variable
build/installation instructions
Merge pull request #4 from chorny/master

upgrade Makefile.PL
bugfix in libiomux
the pruning counter is not very interesting
minor cleaning
allow to use the LIBDIR and INCDIR env variables as overrides
new spec for the version 2 of the protocol

some new messages have been introduced and GET returns now an extra record
(which can still safely ignored by older protocol implementations)
minor changes to the spec
definitions for the new messages
introducing shardcache_get_multi() arc_lookup_multi() and arc_lookup_nofetch()

on the way of supporting GET_MULTI commands down to the storage level

(for now implementing the support at the cache level)
some more work (still in progress)
mark the "missing" objects as being locked (they are going to be fetched straightaway)

+ minor tweaks
extending the definition of the SET command by adding an new optional parameter

which, if present and not-zero, determines the cache-expiration time for the newly set key.
allow to force/set the cache expiration time when using the shardcache_set_async() interface
more notes
ensure using uint64_t instead of size_t

to store the lists size (and related counters) in the underlying arc implementation
fixed the documentation for the fetch_multi callback