mvn should be run in batch mode

[tmagrino]

I noticed something while helping a colleague get set up with eclim with a maven project that caused :Mvn to not jump to the first build error. Specifically, the current definition in https://github.com/ervandew/eclim/blob/master/org.eclim.jdt/vim/eclim/compiler/eclim_mvn.vim does not currently use the flag -B (for batch mode). Without this flag, output from mvn will be colorized and not match the errorformat patterns defined in https://github.com/ervandew/eclim/blob/master/org.eclim.jdt/vim/eclim/compiler/eclim_mvn.vim.

[tmagrino]

Actually a better flag, if the mvn installation being used is new enough, would be --color=disabled as discussed here https://issues.apache.org/jira/browse/MNG-6220