BLD: use mpl 1.1.1 in python 2.7 production travis build

Author: cpcloud

ci/requirements-2.7.txt

@@ -6,7 +6,7 @@ cython==0.19.1
 bottleneck==0.6.0
 numexpr==2.1
 tables==2.3.1
-matplotlib==1.2.1
+matplotlib==1.1.1
 openpyxl==1.6.2
 xlrd==0.9.2
 patsy==0.1.0