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.
Something not greatMerge branch 'malte' into cost_model

Conflicts:
	src/base/Makefile
	src/engine/Makefile
	src/scheduling/Makefile
	src/scheduling/dimacs_exporter_test.cc
	src/scheduling/flow_graph.cc
	src/scheduling/flow_graph_test.cc
Merge branch 'cost_model' of https://github.com/gustafa/firmament into cost_model