open up our ccache a bit, try to cache apt pkgs

.travis.yml

@@ -14,7 +14,8 @@ env:
 git:
   quiet: true
 before-install: 
-  - ccache --set-config=compiler_check=content
+  - ccache --set-config=compiler_check=content -M 5G -F 0
+
 install:
   - git clone --depth 1 --recurse-submodules https://github.com/keyboardio/Kaleidoscope-Bundle-Keyboardio ../hardware/keyboardio
 ## We delete the Bundle's version of Kaleidoscope, and symlink ourselves in.
@@ -29,6 +30,7 @@ notifications:
     on_success: change
     on_failure: change
 cache:
+  apt: true
   ccache: true
   directories:
     - .ccache