Update travis

Author: Dmitry Yashunin

.travis.yml

@@ -1,12 +1,30 @@
 language: python
 
-os:
-  - linux
-  - windows
-  
-python:
-  - '3.6'
-  - '3.7'
+jobs:
+  include:
+    - name: Linux Python 3.6
+      os: linux
+      python: 3.6
+    
+    - name: Linux Python 3.7
+      os: linux
+      python: 3.7
+    
+    - name: Windows Python 3.6
+      os: windows
+      language: shell    # 'language: python' is an error on Travis CI Windows
+      before_install:
+        - choco install python --version 3.6.0
+        - python -m pip install --upgrade pip
+      env: PATH=/c/Python36:/c/Python36/Scripts:$PATH
+    
+    - name: Windows Python 3.7
+      os: windows
+      language: shell    # 'language: python' is an error on Travis CI Windows
+      before_install:
+        - choco install python --version 3.7.0
+        - python -m pip install --upgrade pip
+      env: PATH=/c/Python37:/c/Python37/Scripts:$PATH
 
 install:
   - |