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/templates/timeline.html

@@ -1,49 +0,0 @@
-{% extends "layout.html" %}
-{% block title %}
-  {% if request.endpoint == 'public_timeline' %}
-    Public Timeline
-  {% elif request.endpoint == 'user_timeline' %}
-    {{ profile_user.username }}'s Timeline
-  {% else %}
-    My Timeline
-  {% endif %}
-{% endblock %}
-{% block body %}
-  <h2>{{ self.title() }}</h2>
-  {% if g.user %}
-    {% if request.endpoint == 'user_timeline' %}
-      <div class="followstatus">
-      {% if g.user.user_id == profile_user.user_id %}
-        This is you!
-      {% elif followed %}
-        You are currently following this user.
-        <a class="unfollow" href="{{ url_for('unfollow_user', username=profile_user.username)
-          }}">Unfollow user</a>.
-      {% else %}
-        You are not yet following this user.
-        <a class="follow" href="{{ url_for('follow_user', username=profile_user.username)
-          }}">Follow user</a>.
-      {% endif %}
-      </div>
-    {% elif request.endpoint == 'timeline' %}
-      <div class="twitbox">
-        <h3>What's on your mind {{ g.user.username }}?</h3>
-        <form action="{{ url_for('add_message') }}" method="post">
-          <p><input type="text" name="text" size="60"><!--
-          --><input type="submit" value="Share">
-        </form>
-      </div>
-    {% endif %}
-  {% endif %}
-  <ul class="messages">
-  {% for message in messages %}
-    <li><img src="{{ message.email|gravatar(size=48) }}"><p>
-      <strong><a href="{{ url_for('user_timeline', username=message.username)
-      }}">{{ message.username }}</a></strong>
-      {{ message.text }}
-      <small>&mdash; {{ message.pub_date|datetimeformat }}</small>
-  {% else %}
-    <li><em>There's no message so far.</em>
-  {% endfor %}
-  </ul>
-{% endblock %}