xF2 Add-on SparkPost Mail Transport 1.1.0

This update makes important changes to prepare sites for upgrade to XenForo v2.2

Important: before upgrading your forum to XF v2.2, make sure you are running v1.1.0 of this addon, then immediately after upgrading to XF v2.2, upgrade this addon to v2.0 - available here:

Changes in v1.1.0:

• rename apikey parameter in preparation for XF 2.2 upgrade and addon v2.x
• put in checks to ensure code isn't called if SparkPost isn't configured
• disable sparkpost if we're still running this version of the addon after upgrading to XF 2.2 to prevent breaking the forum

Minor update to prevent v1.0.2 being installed on XF 2.2 which is not compatible (new version of addon with XF 2.2 compatibility coming shortly)

Anyone already running v1.0.1 on XF 2.1 does not need to upgrade to this version.

Very minor bugfix: removed unused variable which was causing E_NOTICEs