ACCUMULO-935 Apply README patch from David Medinets, with my modifications for clarity and to expand on the behavior of DEV_ACCUMULO_HOME

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1489956 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1070 cleaned up warnings

git-svn-id: https://svn.apache.org/repos/asf/accumulo/trunk@1489982 13f79535-47bb-0310-9956-ffa450edef68