Update README.txt

if run "mvn install" in the core directory,when run "mvn jetty:run" in the web directory will get "Could not find artifact com.mycompany:myproject-core:jar:1.0-SNAPSHOT in appfuse-snapshots " error.there is no myproject-1.0-SNAPSHOT.pom in the .m2\repository. when i run "mvn install" in the root directory. "mvn jetty:run" works.