fix typo (#629)

Author: xuwei-k

handlebars/src/main/java/com/github/jknack/handlebars/Options.java

@@ -581,7 +581,7 @@ public CharSequence apply(final Template template) throws IOException {
    *
    * @param <T> The runtime type.
    * @param index The parameter position.
-   * @return The paramater's value.
+   * @return The parameter's value.
    */
   @SuppressWarnings("unchecked")
   public <T> T param(final int index) {
@@ -606,7 +606,7 @@ public <T> T param(final int index) {
    * @param index The parameter position.
    * @param defaultValue The default value to return if the parameter is not
    *        present or if null.
-   * @return The paramater's value.
+   * @return The parameter's value.
    */
   @SuppressWarnings("unchecked")
   public <T> T param(final int index, final T defaultValue) {