vagrant setup in order to be able to test it on mono

In order to simplify testing on mono you might want something like this.

to build and run do a vagrant ssh and then

    xbuild src/log4net.ElasticSearch.sln
    mono --runtime=v4.0 ./src/packages/xunit.runners.1.9.2/tools/xunit.console.exe ./src/log4net.ElasticSearch.Tests/bin/Debug/log4net.ElasticSearch.Tests.dll