Update CMakeLists.txt
Merge pull request #40 from MichaelRuhnke/patch-1

Update CMakeLists.txt
Thx :-)
removing using namespace from all headers

fix for #42
Merge branch 'master' into unit_test

Conflicts:
	g2o/types/slam3d/test_isometry3d_mappings.cpp
	g2o/types/slam3d/test_slam3d_jacobian.cpp
	unit_test/slam3d/jacobians_slam3d.cpp