Use index.html instead of example-list.html

The original decision to avoid index.html was because it only works with a build step.  Since we've all accepted a build step, the more sensible name is index.html.  Without this change, every hosted example has a link to http://openlayers.github.com/ol3/master/examples/example-list.html which 404s.

bin/example-screenshot.js

@@ -42,7 +42,7 @@
       exampleDir = system.args[2],
       // various settings
       ignoreFiles = [
-        'example-list.html'
+        'index.html'
       ],
       intervalMillisecs = 25,
       renderMillisecs = 2000,

bin/exampleparser.py

@@ -38,11 +38,11 @@ feedPath = "http://openlayers.github.com/ol3/master/examples/"
 def getListOfExamples(relPath):
     """
     returns list of .html filenames within a given path - excludes
-    example-list.html
+    index.html
     """
     examples = os.listdir(relPath)
     examples = [example for example in examples if
-                example.endswith('.html') and example != "example-list.html"]
+                example.endswith('.html') and example != "index.html"]
     return examples