release v2.1.0

features: collection services are now public

versions

Set correct version dependecies

Remove private repo info + set locks

Lock at 2.0.0 for tag

Remove private repo

Lock dependency on v1.5.0

As it's only a dependency to run the tests, include it in the dev req…

…uirements instead

Now with unit tests; Had to require expression language component for…

… some reason even though it should be bundled in Symfony itself

Merged in PS-583 (pull request #1)

PS-583

Approved-by: Robert Szeker