Added travis status to readme

Author: lindonroberts

README.rst

@@ -1,6 +1,6 @@
-===================================================================================
-Py-BOBYQA: Derivative-Free Solver for Bound-Constrained Minimization |PyPI Version|
-===================================================================================
+==================================================================================================
+Py-BOBYQA: Derivative-Free Solver for Bound-Constrained Minimization |Build Status| |PyPI Version|
+==================================================================================================
 Py-BOBYQA is a flexible package for solving bound-constrained general objective minimization, without requiring derivatives of the objective. It is a Python implementation of the BOBYQA algorithm by Powell. Py-BOBYQA is particularly useful when evaluations of the objective function are expensive and/or noisy.
 
 More details about Py-BOBYQA can be found in our paper: C. Cartis, J. Fiala, B. Marteau and L. Roberts, Improving the Flexibility and Robustness of Model-Based Derivative-Free Optimization Solvers, technical report, University of Oxford, (2018).
@@ -102,5 +102,7 @@ License
 -------
 This algorithm is released under the GNU GPL license.
 
+.. |Build Status| image::  https://travis-ci.org/numericalalgorithmsgroup/pybobyqa.svg?branch=master
+                  :target: https://travis-ci.org/numericalalgorithmsgroup/pybobyqa
 .. |PyPI Version| image:: https://img.shields.io/pypi/v/Py-BOBYQA.svg
                   :target: https://pypi.python.org/pypi/Py-BOBYQA