Changed to Python 2.7 for Readthedocs builds.

docs/.environment.yml

@@ -3,21 +3,20 @@ channels:
 - defaults
 dependencies:
 - ca-certificates=2017.08.26=ha1e5d58_0
-- certifi=2017.11.5=py36ha569be9_0
+- certifi=2017.11.5=py27hfa9a1c4_0
 - libcxx=4.0.1=h579ed51_0
 - libcxxabi=4.0.1=hebd6815_0
 - libedit=3.1=hb4e282d_0
 - libffi=3.2.1=h475c297_4
 - ncurses=6.0=hd04f020_2
 - openssl=1.0.2n=hdbc3d79_0
-- pip=9.0.1=py36h1555ced_4
-- python=3.6.4=hc167b69_1
+- pip=9.0.1=py27h1567d89_4
+- python=2.7.14=hde5916a_29
 - readline=7.0=hc1231fa_4
-- setuptools=38.4.0=py36_0
+- setuptools=38.4.0=py27_0
 - sqlite=3.20.1=h7e4c145_2
 - tk=8.6.7=h35a86e2_3
-- wheel=0.30.0=py36h5eb2c71_1
-- xz=5.2.3=h0278029_2
+- wheel=0.30.0=py27h677a027_1
 - zlib=1.2.11=hf3cbc9b_2
 prefix: //anaconda/envs/docs