update travis script

Author: chfw

.moban.d/travis.yml

@@ -10,5 +10,5 @@
   - 3.5
 {%endblock%}
 
-{% block custom_install %}  - pip install pyramid==PYRAMID_VERSION
+{% block custom_install %}  - pip install pyramid==$PYRAMID_VERSION
 {% endblock%}

.travis.yml

@@ -12,7 +12,7 @@ python:
   - 3.4
   - 3.5
 install:
-  - pip install pyramid==PYRAMID_VERSION
+  - pip install pyramid==$PYRAMID_VERSION
   - pip install -r requirements.txt
   - pip install -r tests/requirements.txt
 script: