cleaned up tests package structure
fixes the play 'race-condition' issue described in #82
not sure I like the package name scala.slick.session, but according to the comment, it has to be there? anyways, as long as it is there, it is better if it is easy to spot
bumping versions
refactored package and fixed deprications in #82.

following code style and best practices to enhance readability.
formatting
now we use a better default execution context