Added a gradle build in order to test the fix

With the current moxie master, the build doesn't succeed.
Do this to execute the gradle build:

 1. Start the moxie proxy
   cd proxy
   rm -rf moxie
   ant run

 2. Start the gradle build
   cd src/test/gradle/010-slf4j
   rm -rf ../gradle-user-home
   gradle --gradle-user-home $(pwd)/../gradle-user-home test

On linux, there is a script doing all of this:

   ./src/test/gradle/run-gradle-tests.sh

The build "gradle test" hangs here:

   ...
   :compileJava
   Download http://repo1.maven.org/maven2/org/slf4j/slf4j-api/1.7.5/slf4j-api-1.7.5.pom
   Download http://repo1.maven.org/maven2/org/slf4j/slf4j-parent/1.7.5/slf4j-parent-1.7.5.pom
   > Building > :compileJava > Resolving dependencies ':compile'

The output of "cd proxy; ant run" is this:

   ...
   [mx:run] Download status: 200
   [mx:run] Content: 2689 bytes; text/xml
   [mx:run] Got request for http://repo1.maven.org/maven2/org/slf4j/slf4j-parent/1.7.5/slf4j-parent-1.7.5.pom
   [mx:run] Downloading to /home/uli/git/moxie/proxy/moxie/remote/repo1.maven.org_maven2/org/slf4j/slf4j-parent/1.7.5/slf4j-parent-1.7.5.pom
   [mx:run] Download status: 200
   [mx:run] Content: 11804 bytes; text/xml
   [mx:run] Found no URL to download in request:
   [mx:run] HEAD http://repo1.maven.org/maven2/org/slf4j/slf4j-parent/1.7.5/slf4j-parent-1.7.5.jar HTTP/1.1
   [mx:run] Accept-Encoding: gzip,deflate
   [mx:run] Host: repo1.maven.org
   [mx:run] Proxy-Connection: Keep-Alive
   [mx:run] User-Agent: Gradle/1.8-rc-1 (Linux;3.11.0-031100-generic;amd64) (Sun Microsystems Inc.;1.6.0_27;20.0-b12)
   [mx:run]
   [mx:run] indexing moxie/remote/repo1.maven.org_maven2/org/slf4j/slf4j-api/1.7.5/slf4j-api-1.7.5.pom
   [mx:run] indexing moxie/remote/repo1.maven.org_maven2/org/slf4j/slf4j-parent/1.7.5/slf4j-parent-1.7.5.pom

A patch for the issue will follow soon. I do have one available, I just
have to do some cleanup on it...