fix fenics installation

python3.yml

@@ -4,12 +4,12 @@ channels:
 dependencies:
   # general numerics (version controlled)
   - python=3.6*
-  - numpy=1.14*
+  - numpy=1.13*
   - scipy=1.0*
   - kwant=1.3*
   # fenics
-  - fenics=2016.2*
-  - mshr=2016.2*
+  - fenics=2018.2*
+  - mshr=2018.2*
   # general numerics (without version control)
   - anaconda
   # plotting and serialization