• added option to enable/disable DKIM verification for each account
• JavaScript DNS library: added support to use a proxy
• sign rules: updated default rules (added firefox.com)
• DKIM key: empty, but existing DNS record is now treated as a missing key instead as an ill-formed one
• fixed installing problem if extensions.getAddons.cache.enabled is set to false (https://bugzilla.mozilla.org/show_bug.cgi?id=1187725) (#65)