Removing default `= null` from properties

See feedback on doctrine/cache#37
Remove dead config
Remove unused var
Remove not needed stuff from PHPUnit bootstrap
Merge pull request #42 from JeroenDeDauw/tests

Remove not needed stuff from PHPUnit bootstrap
Merge pull request #39 from JeroenDeDauw/var

Remove unused var
Merge pull request #40 from JeroenDeDauw/config

Remove dead config
Fixed the creation of the cache directory in case of a race condition.
Fixed race condition when writing  cache on disk
Removed workaround for PHP 5.2
Made diff easier to read
Removed unneeded attribution notices
#38 - applying minor whitespace-based CS fixes
Merge branch 'hotfix/#38-race-conditions-in-filesystem-cache'
Fix ArrayCache::contains

Now returns true for null values
Add test for null values.
Merge pull request #45 from TimeToogo/master

Fix handling of null values
Adding `composer.lock` to ignores (not a deployable project)
Add visibility keywords to the interface
Merge pull request #47 from dunglas/patch-1

Add visibility keywords to the interface
Bugfix: Fully clearing cache on doFlush()

Second parameter of xcache_clear_cache function indicates which chunk of cache to clear. Since doFlush() should clear entire cache the second parameter should be either omitted or set to -1 (http://xcache.lighttpd.net/wiki/XcacheApi)