RF: further simplify Appveyor file

Remove quotes that may not be necessary.

appveyor.yml

@@ -1,35 +1,34 @@
 # vim ft=yaml
 # CI on Windows via appveyor
-# This file was based on Olivier Grisel's python-appveyor-demo
 
 environment:
 
   matrix:
-    - PYTHON: "C:\\Python27"
-    - PYTHON: "C:\\Python27-x64"
-    - PYTHON: "C:\\Python34"
-    - PYTHON: "C:\\Python34-x64"
-    - PYTHON: "C:\\Python35"
-    - PYTHON: "C:\\Python35-x64"
-    - PYTHON: "C:\\Python36"
-    - PYTHON: "C:\\Python36-x64"
+    - PYTHON: C:\Python27
+    - PYTHON: C:\Python27-x64
+    - PYTHON: C:\Python34
+    - PYTHON: C:\Python34-x64
+    - PYTHON: C:\Python35
+    - PYTHON: C:\Python35-x64
+    - PYTHON: C:\Python36
+    - PYTHON: C:\Python36-x64
 
 install:
   # Prepend newly installed Python to the PATH of this build (this cannot be
   # done from inside the powershell script as it would require to restart
   # the parent CMD process).
-  - "SET PATH=%PYTHON%;%PYTHON%\\Scripts;%PATH%"
+  - SET PATH=%PYTHON%;%PYTHON%\Scripts;%PATH%
 
   # Install the dependencies of the project.
-  - "pip install numpy scipy matplotlib nose h5py mock"
-  - "pip install pydicom"
-  - "python setup.py install"
-  - "SET NIBABEL_DATA_DIR=%CD%\\nibabel-data"
+  - pip install numpy scipy matplotlib nose h5py mock
+  - pip install pydicom
+  - pip install .
+  - SET NIBABEL_DATA_DIR=%CD%\nibabel-data
 
 build: false  # Not a C# project, build stuff at the test step instead.
 
 test_script:
   # Change into an innocuous directory and find tests from installation
-  - "mkdir for_testing"
-  - "cd for_testing"
-  - "nosetests --with-doctest nibabel"
+  - mkdir for_testing
+  - cd for_testing
+  - nosetests --with-doctest nibabel