No jira: add note to site doc to help me remember to set M2_HOME.


git-svn-id: https://svn.apache.org/repos/asf/maven/release/trunk@1624763 13f79535-47bb-0310-9956-ffa450edef68
no jira: set version 2.6.0-SNAPSHOT to anticipate an SCM-pickup release.


git-svn-id: https://svn.apache.org/repos/asf/maven/release/trunk@1624766 13f79535-47bb-0310-9956-ffa450edef68