improve index page design

- avoid overlapping in the header bar
- scale down the gopher image to save a bunch of kilobytes
- hide the ethereum logo on smaller screens
- fix indentation

index.html

@@ -60,6 +60,10 @@
       </div>
     </div>
 
+    <div class="container mascot-mobile">
+      <img src="./static/images/mascot.png" height="300px" />
+    </div>
+
     <div class="container marketing">
       <div class="row featurette">
         <div class="col-md-7">
@@ -67,20 +71,17 @@
           <p class="lead">Ethereum is a  decentralized platform that runs smart contracts, applications that run exactly as programmed without possibility of downtime, censorship, fraud or third party interference.</p>
           <p class="lead">See <a href="https://ethereum.org" target="_blank">our website</a> or <a href="http://ethdocs.org/en/latest/introduction/what-is-ethereum.html" target="_blank">read the docs</a> for more infos!</p>
         </div>
-        <div class="col-md-5">
+        <div class="col-md-5 hide-on-small-screen">
           <img class="featurette-image center-block" src="./static/images/ethereum.png" height="300px">
         </div>
       </div>
       <hr/>
       <div class="row featurette">
-        <div class="col-md-7 col-md-push-5">
+        <div class="col-md-7">
           <h2 class="featurette-heading">What is Go Ethereum?</h2>
           <p class="lead">Go Ethereum is one of the three original implementations (along with C++ and Python) of the Ethereum protocol. It is written in Go, fully open source and licensed under the GNU LGPL v3.</p>
           <p class="lead">See <a href="https://github.com/ethereum/go-ethereum" target="_blank">our repository</a> and <a href="./downloads">downloads section</a> for the code!</p>
         </div>
-        <div class="col-md-5 col-md-pull-7">
-          <img class="featurette-image center-block">
-        </div>
       </div>
       <hr/>
       <div class="row featurette">
@@ -89,9 +90,6 @@
           <p class="lead">Go Ethereum is available either as a standalone client called Geth that you can install on pretty much any operating system, or as a library that you can embed in your Go, Android or iOS projects.</p>
           <p class="lead">See our <a href="./install">installation guide</a> or our <a href="./downloads">developer guide</a> for details!</p>
         </div>
-        <div class="col-md-5">
-          <img class="featurette-image center-block">
-        </div>
       </div>
       <hr/>
       <footer>