Move assets on s3 to hosted site (#128)

Author: pierluc-codes

docs/assets/css/style.css

@@ -94,7 +94,7 @@ pre > code {
     padding:10px;
     background-color:#ffc;
     margin-bottom:25px;
-    background-image:url(https://s3.amazonaws.com/lyah/note.jpg);
+    background-image:url(../images/note.png);
 }
 .hintbox > p {
     margin-bottom:0px;
@@ -141,7 +141,7 @@ pre > code {
     margin:0px auto;
 }
 .introcontent {
-    background-image:url(https://s3.amazonaws.com/lyah/bg.png);
+    background-image:url(../images/bg.png);
 }
 .bgwrapper {
     margin-top:50px;
@@ -225,13 +225,13 @@ pre > code {
 }
 .prevlink {
     padding-left:20px;
-    background-image:url(https://s3.amazonaws.com/lyah/prv.png);
+    background-image:url(../images/prv.png);
     background-position:0px 3px;
     background-repeat:no-repeat;
 }
 .nxtlink {
     padding-right:20px;
-    background-image:url(https://s3.amazonaws.com/lyah/nxt.png);
+    background-image:url(../images/nxt.png);
     background-position:top right;
     background-repeat:no-repeat;
 }

docs/assets/images/bg.png

@@ -24,7 +24,7 @@ Every time a number is encountered, push it onto the stack.
 When we encounter an operator, take the two numbers that are on top of the stack (we also say that we *pop* them), use the operator and those two and then push the resulting number back onto the stack.
 When you reach the end of the expression, you should be left with a single number if the expression was well-formed and that number represents the result.
 
-![this expression](http://s3.amazonaws.com/lyah/rpn.png){.center width=626 height=224}
+![this expression](assets/images/functionally-solving-problems/rpn.png){.center width=626 height=224}
 
 Let's go over the expression `10 4 3 + 2 * -` together!
 First we push `10` onto the stack and the stack is now `10`.