Improved the "definition overriding" documentation

Update the requirement of Invoker

Fixes bug PHP-DI#240 A parent definition could be erased if no defini…

…tion with the same name exist in sub-source

Fixes PHP-DI#222 Bug when using a cache and manually setting a defini…

…tion

PHP-DI#216 Improved test

Merge pull request PHP-DI#210 from mnapoli/test-factory-definition-re…

…solver

Possible fatal error on PHP 5.3 in FactoryDefinitionResolver

Fixed phpdoc that was lost on DI\* functions because of 0e267e2

Fixes PHP-DI#201: Rare cases where "functions.php" is included twice …

…leads to error

Added directories to exclude from the distribution

"Getting started" update