update documentation (#16)

Author: cle-b

docs/image.md

@@ -20,7 +20,7 @@ These methods have the same behavior than the classic `find_element` methods but
 
 They take only one argument which is the path to the PNG image that you search.
 
-## Find element by image
+## Find image
 
 The methods `find_image` and `find_images` are available only from the `WebDriver` object. Only the visible page is analyzed in order to locate the image.
 

mkdocs.yml

@@ -5,7 +5,7 @@ repo_url: https://github.com/cle-b/niobium
 
 nav:
     - Niobium: index.md
-    - Find Element by Image: image.md
+    - Find Image: image.md
     - WebElement new actions: webelement_action.md
     - WebElement wait expected conditions: webelement_wait.md