Pipeline requests in get_multi

Instead of doing lot's of small writes do 1 larger write. This also
considerably cuts down on locking already locked servers.
Keep existing behaviour when no server is found
Debug message instead of warning

Closer to old behaviour
Make get_multi go through chokepoint method
Merge branch 'faster_get_multi_rebased' of git://github.com/xaop/dalli into xaop-faster_get_multi_rebased
Update changes, version
Something a little more helpful
Convert from mini_shoulda to plain ole minitest
Changed canoncail exmaples to include keepalive, I believe this should be better starting point for majority of usages.
fix memcache add command after LocalStore broke it

- add a breaking spec for write(unless_exist:true)
- clear LocalCache on write(unless_exist)
- update changelog with info in unless_exist fix
Merge pull request #365 from pitr/fix-unless_exist

ADD - or `write(unless_exist:true)` -  is broken due to LocalStore
Merge pull request #366 from AvnerCohen/canonical_examples

Changed canoncail exmaples to include keepalive.
Fix shadowed variables
oops
Write failure exceptions to log
Also log state verification failures
Make state verification failures more descriptive
Don't include backtrace in failure log output
Make exception a required argument to failure!
Merge pull request #368 from akahn/log_failures

Include reason for failure in log