Adding maven version to the list of default Grok patterns (#130)

* Adding maven version to the list of default Grok patterns
* Create maven file and put its regex in it
* Add maven regex test

patterns/maven

@@ -0,0 +1 @@
+MAVEN_VERSION (?:(\d+)\.)?(?:(\d+)\.)?(\*|\d+)(?:[.-](RELEASE|SNAPSHOT))?

spec/patterns/maven_spec.rb

@@ -0,0 +1,61 @@
+# encoding: utf-8
+require "spec_helper"
+require "logstash/patterns/core"
+
+describe "MAVEN_VERSION" do
+
+  let(:pattern) { 'MAVEN_VERSION' }
+
+  context "when maven version is simple" do
+    let(:value) { '1.1.0' }
+
+    it "should match the version" do
+      expect(grok_match(pattern,value)).to pass
+    end
+  end
+
+  context "when maven version is a bit more complex" do
+    let(:value) { '2.35.128' }
+
+    it "should match the version" do
+      expect(grok_match(pattern,value)).to pass
+    end
+  end
+
+  context "when maven version contains release" do
+    let(:value) { '1.1.0.RELEASE' }
+
+    it "should match the version" do
+      expect(grok_match(pattern,value)).to pass
+    end
+  end
+
+  context "when maven version contains shapshot" do
+    let(:value) { '1.1.0.SNAPSHOT' }
+
+    it "should match the version" do
+      expect(grok_match(pattern,value)).to pass
+    end
+  end
+
+  context "when maven version contains release" do
+    context "and the version contains a dash" do
+      let(:value) { '1.1.0-RELEASE' }
+
+      it "should match the version" do
+        expect(grok_match(pattern,value)).to pass
+      end
+    end
+  end
+
+  context "when maven version contains shapshot" do
+    context "and the version contains a dash" do
+    let(:value) { '1.1.0-SNAPSHOT' }
+
+      it "should match the version" do
+        expect(grok_match(pattern,value)).to pass
+      end
+    end
+  end
+
+end