WP compatibility

Please update the compatibility of Sparkpost plugin.

Tried on my website with 4.2.4 and the HTTP API did work but made it weird – double email, not all addtesses. Updated to 4.4.2 and now everything seems OK.

Don’t know when wordpress HTTP API was changed, but that is used by Sparkpost, so if any weird sending issues, then just update.

https://wordpress.org/plugins/sparkpost/