Merge pull request #62 from JordanMartinez/nonNullValues

Added convenience method: non-null values of Val

Author: TomasMikula

reactfx/src/main/java/org/reactfx/value/Val.java

@@ -123,6 +123,15 @@ default EventStream<T> values() {
         return EventStreams.valuesOf(this);
     }
 
+    /**
+     * Returns a stream of non-null values of this {@linkplain Val}. The returned stream
+     * emits the current value of this {@linkplain Val} if it is not null for each new subscriber
+     * and then the new value if it is not null whenever the value changes.
+     */
+    default EventStream<T> nonNullValues() {
+        return EventStreams.nonNullValuesOf(this);
+    }
+
     /**
      * Checks whether this {@linkplain Val} holds a (non-null) value.
      * @return {@code true} if this {@linkplain Val} holds a (non-null) value,