Merge pull request #12 from gustafa/malte

Merge @gustafa's fix for pion compilation with C++11 enabled for the main build. (Since we link pion statically, the C++ ABIs must be the same.)
[build] Build in C++11 mode if we have Boost 1.55 available.
[base] [engine] [scheduling] Conditional use of C++11 features based on whether we are doing a C++11 build.
[build] Fix parallel build (issue #9).
[build] Remove debug output on rules.
[build] Add missing boost-filesystem dependency.
Fixing Pion issue, now building with Clang and c++11 support.