Fix for caching error

After the cache file was generated, it wasn't possible to switch the lowercase option anymore. Now the data are always cached with camel-case keys, and modified to lowercase after reading the cache in the getBrowser() method.
Merge pull request #25 from ziege/patch-1

Fix for caching error
Merge branch 'master' of https://github.com/browscap/browscap-php into file-locking