Fix rockspec version format

Author: pintsized

lua-resty-http-0.17.0-beta.1-0.rockspec renamed to lua-resty-http-0.17.0.beta.1-0.rockspec

@@ -1,5 +1,5 @@
 package = "lua-resty-http"
-version = "0.17.0-beta.1-0"
+version = "0.17.0.beta.1-0"
 source = {
     url = "git://github.com/ledgetech/lua-resty-http",
     tag = "v0.17.0-beta.1"