#831 Implement single session by canceling kicks caused by same name joining

- A little less nice, but works on both CraftBukkit and Spigot
- Remove obsolete warning

src/test/java/fr/xephi/authme/util/ServerUtilsTest.java

@@ -1,19 +0,0 @@
-package fr.xephi.authme.util;
-
-import org.junit.Test;
-
-import static org.hamcrest.Matchers.equalTo;
-import static org.junit.Assert.assertThat;
-
-/**
- * Test for {@link ServerUtils}.
- */
-public class ServerUtilsTest {
-
-    @Test
-    public void shouldReturnTrueForSpigotImplementation() {
-        // Spigot is a provided dependency of the project, so the ClassLoader knows about it
-        assertThat(ServerUtils.isSpigot(), equalTo(true));
-    }
-
-}