Removed unused imports.

theano/gradient.py

@@ -21,8 +21,6 @@ from itertools import izip
 from theano import gof
 from theano.gof import Variable
 from theano.gof.python25 import OrderedDict
-from theano.gof.python25 import all
-import theano.gof.utils
 from theano.gof.null_type import NullType
 from theano.printing import min_informative_str
 # we can't do "import theano.tensor"