- set parallelExceution to false for diffrent scopes

There is still a problem with travis builds sometimes that cause the play test run to fail with
Could not create directory /home/travis/build/pussinboots/bankapp/target/scala-2.10/classes.bak
exception. Try to fix it by setting parallelexceution to false for different sbt tasks see below
parallelExecution in Test := false
parallelExecution in ScctTest := false
parallelExecution in ScoverageSbtPlugin.scoverageTest := false