Set optional dependency pyasn1 version >=0.1.1

ndg_httpsclient is incompatible with pyasn1 0.0.11a0,
which is shipped with Ubuntu precise.

The next version of pyasn1 0.0.13 is not compatible
with Python 3, so require the next version 0.1.1

Also use a list for the extra dependency.

.travis.yml

@@ -7,5 +7,11 @@ python:
   - 3.5
   - nightly
 script:
-  - python setup.py install
+  - pip install --upgrade pip
+  - |
+    if [[ ${TRAVIS_PYTHON_VERSION:0:1} == '2' ]]; then
+      pip install pyasn1==0.0.11a0
+    fi
   - pip install -e '.[subjectAltName_support]'
+  - (cd /tmp && pip uninstall --yes ndg_httpsclient)
+  - python setup.py install

setup.py

@@ -122,7 +122,7 @@
             ],
     },
     install_requires = ['PyOpenSSL'],
-    extras_require = {'subjectAltName_support': 'pyasn1'},
+    extras_require = {'subjectAltName_support': ['pyasn1>=0.1.1']},
     classifiers = [
         'Development Status :: 3 - Alpha',
         'Environment :: Console',