Profile automation for tests + Travis build.

See https://travis-ci.org/jsha/https-everywhere/builds/32290936 for an example.
```
diff --git a/python-lib/cuddlefish/prefs.py b/python-lib/cuddlefish/prefs.py
index dd2ac8c..527101a 100644
--- a/python-lib/cuddlefish/prefs.py
+++ b/python-lib/cuddlefish/prefs.py
@@ -8,7 +8,7 @@ DEFAULT_COMMON_PREFS = {
     # sets this preference)
     'browser.dom.window.dump.enabled': True,
     # warn about possibly incorrect code
-    'javascript.options.strict': True,
+    'javascript.options.strict': False,
     'javascript.options.showInConsole': True,
 
     # Allow remote connections to the debugger
```