revised travis

.travis.yml

 language: python
-python:
-  - "2.6"
-  - "2.7"
-  - "3.2"
-  - "3.3"
-  - "3.4"
-  - "3.5"
-  - "3.5-dev" # 3.5 development branch
-  - "3.6"
-  - "3.6-dev" # 3.6 development branch
-  - "3.7-dev" # 3.7 development branch
-  - "nightly" # currently points to 3.7-dev
-# command to install dependencies
+
+before_script:
+  - pip install -U pytest
+
+matrix:
+  include:
+    - python: "2.6"
+    - python: "2.7"
+    - python: "3.2"
+    - python: "3.3"
+    - python: "3.4"
+    - python: "3.5"
+    - python: "3.5-dev"
+    - python: "3.6"
+    - python: "3.6-dev"
+    - python: "3.7"
+    - python: "nightly"
+  allow_failures:
+    - python: "3.5-dev"
+    - python: "3.6"
+    - python: "3.6-dev"
+    - python: "3.7"
+    - python: "nightly"
+
 install: "pip install -r requirements.txt"
-# command to run tests
-script: pytest
\ No newline at end of file
+script:
+  - uname -a
+  - pytest --version
+  - pytest
\ No newline at end of file