Load php library via Composer

Problem/Motivation

Right now the module requires to have the php library managed by `libraries`, however if we install the library via composer (and/or via composer_manager → ) it will end up in a different place.
This means that the check in twilio_command will fail to detect the library, because it explicitly checks for libraries_load(TWILIO_LIBRARY), while this could be a fallback check to see if the classes are already loaded.

Proposed resolution

Check if the classes are already loaded in another way (for example autoload.php) before attempting to load via libraries module.

Remaining tasks

• Evaluate possible regressions
• Commit change