Added Gradle / Maven tabs

with these changes if someone is not interested with one of those tools one won't see it until it gets clicked

fixes #152

scripts/generateDocs.sh

@@ -7,7 +7,7 @@ set -e
 echo "Generating docs for Spring Cloud Contract"
 
 echo "Building main docs"
-./mvnw clean install -P docs -DskipTests=true --pl docs
+./mvnw clean install -P docs -DskipTests=true --pl docs-extensions,docs
 
 echo "Building maven plugin docs"
 ./mvnw site -DskipTests=true --pl spring-cloud-contract-tools/spring-cloud-contract-maven-plugin