add more notes about Eclipse setup

- "search for nested projects..."
- amount of memory Eclipse needs to build elasticsearch successfully
- make sure m2e-connector is not installed

CONTRIBUTING.md

@@ -76,7 +76,7 @@ Contributing to the Elasticsearch codebase
 
 **Repository:** [https://github.com/elasticsearch/elasticsearch](https://github.com/elastic/elasticsearch)
 
-Make sure you have [Maven](http://maven.apache.org) installed, as Elasticsearch uses it as its build system. Integration with IntelliJ and Eclipse should work out of the box. Eclipse users can automatically configure their IDE by running `mvn eclipse:eclipse` and then importing the project into their workspace: `File > Import > Existing project into workspace`.
+Make sure you have [Maven](http://maven.apache.org) installed, as Elasticsearch uses it as its build system. Integration with IntelliJ and Eclipse should work out of the box. Eclipse users can automatically configure their IDE by running `mvn eclipse:eclipse` and then importing the project into their workspace: `File > Import > Existing project into workspace` and make sure to select `Search for nested projects...` option as Elasticsearch is a multi-module maven project. Additionally you will want to ensure that Eclipse is using 2048m of heap by modifying `eclipse.ini` accordingly to avoid GC overhead errors. Please make sure the [m2e-connector](http://marketplace.eclipse.org/content/m2e-connector-maven-dependency-plugin) is not installed in your Eclipse distribution as it will interfere with setup performed by `mvn eclipse:eclipse`.
 
 Elasticsearch also works perfectly with Eclipse's [m2e](http://www.eclipse.org/m2e/).  Once you've installed m2e you can import Elasticsearch as an `Existing Maven Project`.