Better bigimg support

Add support for bigimg's on the front page, multiple images that rotate
on both the front page and regular pages and posts, also added test
images and a sample to demonstrate the functionality and how to specify
bigimg's.

exampleSite/config.toml

@@ -16,6 +16,16 @@ pygmentCodeFences = true
   rss = true
   comments = true
 
+#[[Params.bigimg]]
+#  src = "img/triangle.jpg"
+#  desc = "Triangle"
+#[[Params.bigimg]]
+#  src = "img/sphere.jpg"
+#  desc = "Sphere"
+#[[Params.bigimg]]
+#  src = "img/hexagon.jpg"
+#  desc = "Hexagon"
+
 [Author]
   name = "Some Person"
   email = "youremail@domain.com"
@@ -50,22 +60,22 @@ pygmentCodeFences = true
     name = "Samples"
     weight = 2
 
+[[menu.main]]
+    parent = "samples"
+    name = "Big Image Sample"
+    url = "/post/2017-03-07-bigimg-sample"
+    weight = 1
+
 [[menu.main]]
     parent = "samples"
     name = "Math Sample"
     url = "/post/2017-03-05-math-sample"
-    weight = 1
+    weight = 2
 
 [[menu.main]]
     parent = "samples"
     name = "Code Sample"
     url = "/post/2016-03-08-code-sample"
-    weight = 2
-
-[[menu.main]]
-    parent = "samples"
-    name = "Test Markdown"
-    url = "/post/2015-02-20-test-markdown"
     weight = 3
 
 [[menu.main]]