changed maven compiler plufin version to 2.5.1 for no particular reason.
changed maven compiler plufin version to 2.5.1 for no particular reason.

redminenb/redmine-java-api,sleroy/redmine-java-api,taskadapter/redmine-java-api,redminenb/redmine-java-api,taskadapter/redmine-java-api,sleroy/redmine-java-api,stephenc/redmine-java-api