minor symfony#73 Use css flexbox for sticky footer. (ogizanagi)

This PR was merged into the master branch.

Discussion
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Use css flexbox for sticky footer.

![screenshot 2015-06-28 a 09 45 51](https://cloud.githubusercontent.com/assets/2211145/8395614/ac9f55fc-1d7b-11e5-9bf5-863339570ea2.PNG)

Commits
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52e0633 Use css flexbox for sticky footer.

Author: javiereguiluz

app/Resources/assets/scss/main.scss

@@ -44,6 +44,14 @@ i {
 // Page elements
 // --------------------------------------------------
 
+body {
+    display: -webkit-flex;
+    display: flex;
+    -webkit-flex-direction: column;
+    flex-direction: column;
+    min-height: 100vh;
+}
+
 // Header
 header {
     margin-bottom: 2em;
@@ -55,7 +63,10 @@ header {
 
 // Body contents
 .body-container {
-    // needed to prevent pages with a very small height
+    -webkit-flex: 1;
+    flex: 1;
+
+    // needed to prevent pages with a very small height and browsers not supporting flex
     min-height: 600px;
 
     #main h1,