Always run composer install (even if a lock file is present)

I'm not sure if I've misunderstood your logic, but I think that the composer_project install action should always run, even if there is a composer.lock file present in the project directory.

Currently, the existence of the lock file is used as a not_if condition but that means the composer_project resource will not install dependencies for example on a build or production machine where the lock file has been checked out from source control.

composer install is idempotent (for the same lock file) so there are no problems with running it multiple times on the same project path.

If there's some issue that I've not appreciated with this change then I could make this a configurable option on the resource (backwards compatible).