Added pandas logo and separator

- Added pandas logo and separator at the top of page

Author: Philip Gura <[email protected]>

Closes pandas-dev#12555 from philipgura/patch-1 and squashes the following commits:

9653ead [Philip Gura] Added pandas logo and separator

Author: philipgura

README.md

@@ -1,3 +1,8 @@
+<div align="center">
+  <img src="http://pandas.pydata.org/_static/pandas_logo.png"><br>
+</div>
+-----------------
+
 # pandas: powerful Python data analysis toolkit
 
 <table>