Update minitwit & improve testing for examples (#1954)

* Update minitwit & improve testing for examples

* Related to #1945
* Re-works minitwit to be installed and run as:

    pip install --editable .
    export FLASK_APP=minitwit.minitwit
    export FLASK_DEBUG=1
    flask initdb
    flask run

* added flaskr and minitwit to norecursedirs
  * tests not properly run when using pytest standards
  * see: http://stackoverflow.com/questions/38313171/configuring-pytest-with-installable-examples-in-a-project
* Both flaskr and minitwit now follow pytest standards.
* Tests can for them as `py.test` or `python setup.py test`

* Update minitwit readme

* updates the instructions for running

* Fixes for updating the minitwit example

- This reverts the changes to the *docs/* (I will file separate PR).
- Running the app is now: `export FLASK_APP=minitwit` & `flask run`
  (After installing the app)

* Remove unnecessary comma from flaskr/setup.py

examples/minitwit/setup.py

@@ -0,0 +1,16 @@
+from setuptools import setup
+
+setup(
+    name='minitwit',
+    packages=['minitwit'],
+    include_package_data=True,
+    install_requires=[
+        'flask',
+    ],
+    setup_requires=[
+        'pytest-runner',
+    ],
+    tests_require=[
+        'pytest',
+    ],
+)