Nuke SteepFunction

LinearFunction<100> serves the save purpose

src/test-gradient-method-nicefunction.hh

@@ -73,15 +73,6 @@ template <int slope> class SampleFunction : public MyFunction {
   }
 };
 
-class SteepFunction : public MyFunction {
-public:
-  double virtual evaluate(double x) const { return 100 * x; }
-
-  double virtual leftDifferential(double s) const { return 100; }
-
-  double virtual rightDifferential(double s) const { return 100; }
-};
-
 // slope in [n-1,n] is n
 class HorribleFunction : public MyFunction {
   // TODO: Handle kinks