could not use scalaj-http interpreter

```
java.lang.NoClassDefFoundError: java.net.Proxy is a restricted class. Please see the Google  App Engine developer's guide for more details.
        at com.google.appengine.tools.development.agent.runtime.Runtime.reject(Runtime.java:51)
        at scalaj.http.Http$Request$.apply$default$7(Http.scala:101)
        at scalaj.http.Http$Request$.apply(Http.scala:96)
        at scalaj.http.Http$.get(Http.scala:281)
        at scalaj.http.Http$.apply(Http.scala:90)
        at ghscala.ScalajHttp$.apply(ScalajHttp.scala:10)
        at ghscala.Core$.get(Core.scala:12)
        at ghscala.Github$.<init>(Github.scala:13)
        at ghscala.Github$.<clinit>(Github.scala)
        at githubtree.GithubApi$.defaultBranch(App.scala:37)
```