Disable N5UniverseImgLoaderTest for now.

It does not pass because of a Java version problem:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:testCompile (default-testCompile) on project mastodon: Compilation failure
[ERROR] /Users/tinevez/Development/MastodonWS/mastodon/src/test/java/org/mastodon/mamut/io/loader/N5UniverseImgLoaderTest.java:[5,43] cannot access uk.org.webcompere.systemstubs.rules.EnvironmentVariablesRule
[ERROR]   bad class file: /Users/tinevez/.m2/repository/uk/org/webcompere/system-stubs-junit4/2.1.3/system-stubs-junit4-2.1.3.jar(uk/org/webcompere/systemstubs/rules/EnvironmentVariablesRule.class)
[ERROR]     class file has wrong version 55.0, should be 52.0
[ERROR]     Please remove or make sure it appears in the correct subdirectory of the classpath.

While @ksugar is working on it, or until the Java version of Fiji is
upgraded, this test is disabled.

src/test/java/org/mastodon/mamut/io/loader/N5UniverseImgLoaderTest.java

@@ -2,11 +2,11 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
-import uk.org.webcompere.systemstubs.rules.EnvironmentVariablesRule;
 
 import java.io.File;
 import java.io.IOException;
 
+import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.mastodon.mamut.ProjectModel;
@@ -16,7 +16,9 @@
 import org.scijava.Context;
 
 import mpicbg.spim.data.SpimDataException;
+import uk.org.webcompere.systemstubs.rules.EnvironmentVariablesRule;
 
+@Ignore
 public class N5UniverseImgLoaderTest
 {