metatag 8.x-1.0-beta8

This release adds a number of additional meta tags, and fixes a few bugs.

Note: Please clear the site's caches after updating to this version.

Full changelog since 8.x-1.0-beta7:

• #2723319 by itmaybejj: Fixed misspelling of 'its'.
• #2619450 by paulmckibben: Remove core's Canonical URL tag if Metatag is adding one.
• #2712277 by markdorison: Twitter Card Type meta tag wasn't updating.
• #2650408 by Raphael Apard, DamienMcKenna, gaurav.goyal, dpacassi, kyberman: A node's meta tags should not override the front page defaults unless the defaults are disabled/deleted.
• #2684479 by mikeyk, DamienMcKenna, aspilicious: Added 'secure' option as some meta tags require HTTPS URLs.
• #2699297 by DamienMcKenna: Added tests to ensure submodules can be enabled.
• #2663974 by IT-Cru, DamienMcKenna: Added the og 'article' meta tags.
• #2650848 by ivanjaros, DamienMcKenna: Only show appropriate entities in the token browser.
• #2705851 by vasi: Load field definitions, not field values, when getting a list of Metatag fields on an entity.
• #2708511 by DamienMcKenna: Added the referrer meta tag.
• #2563629 by Jim.M, DamienMcKenna: Added site verification tags.
• #2721857 by marvin_B8, DamienMcKenna: Added Google+ meta tags.