Undo change to revolute joint rand_configuration distribution.

Probably too many things tacitly assume this distribution at some point.

Should revisit as part of #459, but we shouldn't introduce backwards
incompatible changes right now.

src/joint_types/revolute.jl

@@ -52,7 +52,7 @@ end
 end
 
 @propagate_inbounds function rand_configuration!(q::AbstractVector, ::Revolute)
-    q[1] = rand(-π : π)
+    q[1] = randn()
     nothing
  end