Update the yum install maven in README

Maven does not install on "yum install maven3" on Fedora20.
Searching for Maven3 package does not give any results.
The correct way to install Maven3 on Fedora is to
run "yum install maven" instead.
This installs Maven3 and its dependencies.

I think we need to update the documentation with that.

Change-Id: Iaf09e0ba8e293c27eaeb5d5c9b75ea18ab94c9e7
Merge "Update the yum install maven in README"