Change generated pom to only generate one jar

WHen using maven-jar-plugins with <executions> there will be two jars,
one from the execution and the one that is automatically generated.
Change the maven-jar-plugin config to simply include
Pact-Assembler-Class in the automatically generated jar.
Add scala quickstart
Add required eclipse plugins to README.md
Merge pull request #3 from aljoscha/master

Fix pom and add scala quickstart