INTTEMPLATES-24 Update SI dep. to 2.2.4.RELEASE

* Update README.md - Add section on Twitter authentication
* Require Twitter authentication for searches (As of Twitter API version 1.1)
* Update Spring dependency to 3.2.3.RELEASE
* Update wro4j dependency to 1.7.0
* Update slf4j-log4j12 dependency to 1.7.5
* Update Jetty Maven Plugin dependency to 8.1.11.v20130520
* Update Maven Compiler Plugin to 3.1
* Upgrade Gradle wrapper to 1.6