Cache some things on CIs.

.appveyor.yml

@@ -1,6 +1,8 @@
 shallow_clone: true
 version: '{branch}-{build}'
-cache: C:\Users\appveyor\pip\wheels
+cache:
+  - C:\projects\qutebrowser\.tox
+  - C:\projects\qutebrowser\.cache
 build: off
 environment:
     PYTHON: 'C:\Python34'

.travis.yml

@@ -7,6 +7,12 @@ os:
 # Not really, but this is here so we can do stuff by hand.
 language: c
 
+cache:
+  directories:
+    - $HOME/.cache/pip
+    - $HOME/build/The-Compiler/qutebrowser/.tox
+    - $HOME/build/The-Compiler/qutebrowser/.cache
+
 install:
   - python scripts/dev/ci_install.py