fixes memcache sessions and cache

[bshaffer]

@tmatsuo @dovy PTAL

@dovy - if you're up to the challenge, pull down my fork with the below commands and see if this works for you:

git checkout -b bshaffer-fixes-memcache-sessions-and-cache master
git pull https://github.com/bshaffer/appengine-symfony-starter-project.git fixes-memcache-sessions-and-cache
composer install

[tmatsuo]

Looks good, I think we should add some tests though. We can add tests later.

[bshaffer]

Absolutely! Added #8

[bshaffer]

@dovy you can just clone the latest branch using the instructions in the README now that this is in master

[dovy]

Yup, worked for me. ;)