Fix PHPOffice#91: Update url of Travis build images

README.md

@@ -1,8 +1,9 @@
 # PHPExcel - OpenXML - Read, Write and Create spreadsheet documents in PHP - Spreadsheet engine
 PHPExcel is a library written in pure PHP and providing a set of classes that allow you to write to and read from different spreadsheet file formats, like Excel (BIFF) .xls, Excel 2007 (OfficeOpenXML) .xlsx, CSV, Libre/OpenOffice Calc .ods, Gnumeric, PDF, HTML, ... This project is built around Microsoft's OpenXML standard and PHP.
 
-Master: [![Build Status](https://secure.travis-ci.org/PHPOffice/PHPExcel.png?branch=master)](http://travis-ci.org/PHPOffice/PHPExcel)
-Develop: [![Build Status](https://secure.travis-ci.org/PHPOffice/PHPExcel.png?branch=develop)](http://travis-ci.org/PHPOffice/PHPExcel)
+Master: [![Build Status](https://travis-ci.org/PHPOffice/PHPExcel.png?branch=master)](http://travis-ci.org/PHPOffice/PHPExcel)
+
+Develop: [![Build Status](https://travis-ci.org/PHPOffice/PHPExcel.png?branch=develop)](http://travis-ci.org/PHPOffice/PHPExcel)
 
 ## File Formats supported