Flush memcache during tearDown steps

This avoids the case where data from a previous test remains persisted and conflicts with subsequent fetch()/contains() of the next test.
File caches should always return boolean values for save()
Extract common setup()/tearDown() for file-based tests
Assert method return values and test additional PHP types in base test
Test deleteAll()/flushAll() behaviors for providers that share storage
Reset namespace version
Merge pull request #22 from FabioBatSilva/namespace_version

Reset namespace version
Merge pull request #18 from doctrine/test-improvements

Test improvements
MongoDB cache provider
Support invalid UTF-8 strings in MongoDB cache provider
Merge pull request #17 from doctrine/mongodb

MongoDB cache provider
Introduce Version class and build system
Update README
Build improvements
Add another fix to CHANGELOG
Fix build.properties
Release 1.2.0
Bump version to 1.2.1
Fix version
Update build.xml