adding package "doParallel" to Imports in DESCRIPTION
adding new argument "parallel" to FlatLineTest() and implement parallel computation of runs
adding new argument "parallel" to ReductiveHourglassTest and implementing parallel computation of runs;

fixing a small bug that caused that the 3 plots that
are drawn when running ReductiveHourglassTest() weren't
displayed on the same plot due to par(mfrow = c(1,2))
instead of par(mfrow = c(1,3))
fixing a small bug in EarlyConservationTest() -> same bug as in ReductiveHourglassTest -> par(mfrow = c(1,2)) was changed to par(mfrow = c(1,3));

adding new argument "parallel" to EarlyConservationTest() for parallel runs execution
adding an abline() to visualize the real hourglass score within the permutation histogram;

updating roxygen documentation from roxygen 4.0.2 to 4.1.0