Added close html filter implementation with Jsoup

src/main/java/com/hubspot/jinjava/lib/filter/CloseHtmlFilter.java

@@ -4,6 +4,8 @@
 import com.hubspot.jinjava.doc.annotations.JinjavaParam;
 import com.hubspot.jinjava.doc.annotations.JinjavaSnippet;
 import com.hubspot.jinjava.interpret.JinjavaInterpreter;
+import java.util.Objects;
+import org.jsoup.Jsoup;
 
 @JinjavaDoc(
   value = "Closes open HTML tags in a string",
@@ -19,10 +21,6 @@ public String getName() {
 
   @Override
   public Object filter(Object var, JinjavaInterpreter interpreter, String... args) {
-    /*
-    Closes open HTML tags.
-     */
-
-    return null;
+    return Jsoup.parse(Objects.toString(var)).toString();
   }
 }

src/test/java/com/hubspot/jinjava/lib/filter/CloseHtmlFilterTest.java

@@ -0,0 +1,24 @@
+package com.hubspot.jinjava.lib.filter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.google.common.collect.ImmutableMap;
+import com.hubspot.jinjava.BaseInterpretingTest;
+import com.hubspot.jinjava.BaseJinjavaTest;
+import org.junit.Before;
+import org.junit.Test;
+
+public class CloseHtmlFilterTest extends BaseInterpretingTest {
+  CloseHtmlFilter f;
+
+  @Before
+  public void setup() {
+    f = new CloseHtmlFilter();
+  }
+
+  @Test
+  public void itClosesTags() {
+    String openTags = "<p>Hello, world!";
+    assertThat(f.filter(openTags, interpreter)).isEqualTo("<p>Hello, world!</p>");
+  }
+}