Add tensorflow to testenv to make builds pass again

Author: dennybritz

tox.ini

@@ -6,6 +6,7 @@ passenv=CIRCLE_ARTIFACTS LD_PRELOAD
 deps=
   nose
   coverage
+  tensorflow
 commands=
   coverage run {envbindir}/nosetests
   coverage report -m
@@ -22,8 +23,10 @@ commands=pylint -E seq2seq
 deps=
   nose
   coverage
+  tensorflow
 
 [testenv:py27]
 deps=
   nose
   coverage
+  tensorflow