haxelib.json: preemptively setting next version to 2.8 to match AS3 version

Author: joshtynjala

haxelib.json

@@ -4,7 +4,7 @@
 	"license": "BSD",
 	"tags": [ "starling", "2d", "gpu", "openfl", "flash", "air", "js", "web", "cpp" ],
 	"description": "The Cross-Platform Game Engine",
-	"version": "2.7.1",
+	"version": "2.8.0",
 	"releasenote": "Adds HashLink target, various bug fixes",
 	"contributors": [
 		"p.j.shand",