Update rebar.config

rebar.config

@@ -1,4 +1,4 @@
 {deps, [
-{cowlib,".*",{git,"https://github.com/ninenines/cowlib","master"}},{ranch,".*",{git,"https://github.com/ninenines/ranch","1.4.0"}}
+{cowlib,".*",{git,"https://github.com/ninenines/cowlib","2.0.0-rc.1"}},{ranch,".*",{git,"https://github.com/ninenines/ranch","1.4.0"}}
 ]}.
 {erl_opts, [debug_info,warn_export_vars,warn_shadow_vars,warn_obsolete_guard,warn_export_all,warn_missing_spec,warn_untyped_record]}.