added instructions how to customize the path for the sqlite-storage file.

closes #12.
Merge pull request #13 from staabm/patch-3

added instructions how to customize the path for the sqlite-storage file.
Major storage refactoring
Fixing query issue with #9
HHVM support
Fixed phpdoc
Merge pull request #17 from staabm/patch-3

Fixed phpdoc
hhvm
Fixing tests
Using installed composer
PHP 5.3
Travis config
added benchmark. closes lstrojny#15