update 'active' version tag

rebar.config

@@ -3,6 +3,6 @@
 {deps_dir,"deps"}.
 {deps, [
     {shen,   ".*", {git, "git://github.com/5HT/shen",           {tag,"1.5.0"}}},
-    {active, ".*", {git, "git://github.com/synrc/active",       {tag,"0.5"}}},
+    {active, ".*", {git, "git://github.com/synrc/active",       {tag,"0.8"}}},
     {avz,    ".*", {git, "git://github.com/synrc/avz",          {tag,"1.4.0"}}}
 ]}.