cmake add all EKF sources (#243)

- trivial cmake cleanup
 - travis-ci build with both gcc and clang
 - update matrix to latest (matches PX4)
 - closes #240

EKF/mathlib.h

@@ -52,7 +52,6 @@
 namespace math
 {
 // using namespace Eigen;
-using namespace std;
 
 float min(float val1, float val2);
 float max(float val1, float val2);
@@ -64,4 +63,4 @@ float degrees(float radians);
 #else
 #include <mathlib/mathlib.h>
 #endif //POSIX_SHARED
-#endif //MATHLIB_H
+#endif //MATHLIB_H