implemented username() method that returns username depending on first and last name (#107)

src/main/java/com/github/javafaker/Name.java

@@ -45,4 +45,12 @@ public class Name {
         return StringUtils.join(new String[] { fakeValuesService.fetchString("name.title.descriptor"),
                 fakeValuesService.fetchString("name.title.level"), fakeValuesService.fetchString("name.title.job") }, " ");
     }
+
+    public String username() {
+        return StringUtils.join(new String[]{
+                firstName().replaceAll("'", "").toLowerCase(),
+                ".",
+                lastName().replaceAll("'", "").toLowerCase()}
+        );
+    }
 }

src/test/java/com/github/javafaker/NameTest.java

@@ -1,11 +1,11 @@
 package com.github.javafaker;
 
-import static com.github.javafaker.matchers.MatchesRegularExpression.matchesRegularExpression;
-import static org.hamcrest.MatcherAssert.assertThat;
-
 import org.junit.Before;
 import org.junit.Test;
 
+import static com.github.javafaker.matchers.MatchesRegularExpression.matchesRegularExpression;
+import static org.hamcrest.MatcherAssert.assertThat;
+
 public class NameTest {
 
     private Faker faker;
@@ -54,4 +54,9 @@ public class NameTest {
     public void testTitle() {
         assertThat(faker.name().title(), matchesRegularExpression("(\\w+\\.?( )?){3}"));
     }
+
+    @Test
+    public void testUsername() {
+        assertThat(faker.name().username(), matchesRegularExpression("^(\\w+)\\.(\\w+)$"));
+    }
 }