Change error message to conform to check_estimator in sklearn 0.19

Author: jcrudy

pyearth/earth.py

@@ -421,7 +421,7 @@ def _scrub_x(self, X, missing, **kwargs):
         # Ensure correct number of columns
         if hasattr(self, 'basis_') and self.basis_ is not None:
             if X.shape[1] != self.basis_.num_variables:
-                raise ValueError('Wrong number of columns in X')
+                raise ValueError('Wrong number of columns in X. Reshape your data.')
 
         # Zero-out any missing spots in X
         if np.any(missing):