use std::back_inserter for appending items via std::copy.
TestCase for multilayerNetwork (LayerTestCase) is failing, because
the initialization step was performed automatically by the optimizer.
For the unit test an explicitly initialization call is necessary.
Remove unnecessary, second find_package(OpenMP) call in CMakeLists.txt
Merge pull request #15 from Ruun/sigma_pi

Bugfixes for SplitableDataSet::merge and TestCase multilayerNetwork