update javadoc of inject and provides (#58)

simple-component/src/main/java/io/jbock/simple/Inject.java

@@ -8,7 +8,18 @@
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
 /**
- * Identifies injectable constructors and <em>static</em> methods.
+ * Identifies injectable constructors and {@code static} methods.
+ * An {@code @Inject}-annotated static method is allowed in the following places:
+ *
+ * <ul>
+ *   <li>The method can be a direct child of the class or interface
+ *     that defines its return type.
+ *   <li>If the class or interface that defines its return type is nested
+ *     inside an enclosing class, then the method may also be a direct child of the
+ *     enclosing class.
+ *   <li>The method can be a direct child of the component interface.
+ *     Alternatively, the {@link Provides} annotation can be used in that case.
+ * </ul>
  */
 @Target({METHOD, CONSTRUCTOR})
 @Retention(RUNTIME)

simple-component/src/main/java/io/jbock/simple/Provides.java

@@ -7,8 +7,8 @@
 import static java.lang.annotation.RetentionPolicy.SOURCE;
 
 /**
- * This is an alternative to the {@code @Inject} annotation
- * which can only be used on static methods directly in the component.
+ * An alternative to the {@code @Inject} annotation that can be used
+ * on static methods which are direct children of the component interface.
  */
 @Target(METHOD)
 @Retention(SOURCE)