Updated website news item with 1.3.1 release

Author: philippjfr

doc/latest_news.html

@@ -7,5 +7,5 @@
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       May 14th 2015: Talk on HoloViews announced at <a href="http://scipy2015.scipy.org/ehome/115969/292868/">SciPy Conference 2015</a>.
       </br>
-      June 27th 2015: HoloViews 1.3.0 released and now available on <a href="https://pypi.python.org/pypi/holoviews/1.3.0">PyPI</a>.
+      July 1st 2015: HoloViews 1.3.1 released and now available on <a href="https://pypi.python.org/pypi/holoviews/1.3.0">PyPI</a>.
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