Fix set mime types (#7)

* Make setMimeTypes public in Displayer API.

This makes Displayer#setMimeTypes public. This was the original intent,
but since the method wasn't public it is technically an API addition.

* Fix tests broken by setMimeTypes change.

* Version 0.2.1.

build.gradle

@@ -2,7 +2,7 @@ apply plugin: 'java'
 apply plugin: 'maven'
 
 group = "jupyter"
-version = '0.1.0'
+version = '0.2.1'
 
 repositories {
   mavenCentral()

src/main/java/jupyter/Displayer.java

@@ -48,6 +48,6 @@ public abstract class Displayer<T> {
    *
    * @param types MIME types that are supported by the kernel
    */
-  void setMimeTypes(String... types) {
+  public void setMimeTypes(String... types) {
   }
 }

src/test/java/jupyter/TestMimeTypeNotification.java

@@ -52,7 +52,7 @@ public Map<String, String> display(String obj) {
     }
 
     @Override
-    void setMimeTypes(String... types) {
+    public void setMimeTypes(String... types) {
       mimeTypes = new HashSet<>(Arrays.asList(types));
     }
   }