Update addProcessor doc example

Calling ``load`` doesn't work because it creates a new loader, ignoring the current one processors (and options).

(See https://github.com/nelmio/alice/blob/master/src/Nelmio/Alice/Fixtures.php#L55)
Authorize magic __call way to populate object
Add a magic __call populator
Merge branch 'devster-1.x' into 1.x
Merging separate magic __call changes from 1.x
Merge branch 'devster-master'
Merge pull request #153 from EmmanuelVella/patch-1

Update addProcessor doc example
updated readme with correct loader documentation
Merge pull request #1 from nelmio/master

Update from original