Address #1902: Converts example/flaskr to have a setup.py (#1945)

* Converts example/flaskr to have a setup.py

Makes the flaskr app easier to run, ex. workflow:
- pip install --editable .
- export FLASK_APP=flaskr.flaskr
- flask initdb
- flask run

Testing is also easier now:
- python setup.py test

* Fixed an import error in flaskr/tests

- the statement `import flaskr` caused errors in python3
- `from . import flaskr` fixes the issue in 2.7.11 and 3.5.1

* Better project structure and updates the docs

- Re-factors *flaskr*'s project structure a bit
- Updates docs to make sense with the new structure
  - Adds a new step about installing Flask apps with setuptools
  - Switches first-person style writing to second-person (reads better IMO)
  - Adds segments in *testing.rst* for running tests with setuptools

* Remove __init__.py from tests

- py.test recommends not using __init__.py

* Fix testing import errors

docs/tutorial/dbinit.rst

@@ -1,6 +1,6 @@
 .. _tutorial-dbinit:
 
-Step 4: Creating The Database
+Step 5: Creating The Database
 =============================
 
 As outlined earlier, Flaskr is a database powered application, and more
@@ -16,13 +16,14 @@ Such a schema can be created by piping the ``schema.sql`` file into the
 
 The downside of this is that it requires the ``sqlite3`` command to be
 installed, which is not necessarily the case on every system.  This also
-requires that we provide the path to the database, which can introduce
+requires that you provide the path to the database, which can introduce
 errors.  It's a good idea to add a function that initializes the database
-for you to the application.
+for you, to the application.
 
-To do this, we can create a function and hook it into the :command:`flask`
-command that initializes the database.  Let me show you the code first.  Just
-add this function below the `connect_db` function in :file:`flaskr.py`::
+To do this, you can create a function and hook it into a :command:`flask`
+command that initializes the database.  For now just take a look at the
+code segment below.  A good place to add this function, and command, is
+just below the `connect_db` function in :file:`flaskr.py`::
 
     def init_db():
         db = get_db()
@@ -38,23 +39,23 @@ add this function below the `connect_db` function in :file:`flaskr.py`::
 
 The ``app.cli.command()`` decorator registers a new command with the
 :command:`flask` script.  When the command executes, Flask will automatically
-create an application context for us bound to the right application.
-Within the function, we can then access :attr:`flask.g` and other things as
-we would expect.  When the script ends, the application context tears down
+create an application context which is bound to the right application.
+Within the function, you can then access :attr:`flask.g` and other things as
+you might expect.  When the script ends, the application context tears down
 and the database connection is released.
 
-We want to keep an actual function around that initializes the database,
+You will want to keep an actual function around that initializes the database,
 though, so that we can easily create databases in unit tests later on.  (For
 more information see :ref:`testing`.)
 
 The :func:`~flask.Flask.open_resource` method of the application object
 is a convenient helper function that will open a resource that the
 application provides.  This function opens a file from the resource
-location (your ``flaskr`` folder) and allows you to read from it.  We are
-using this here to execute a script on the database connection.
+location (the :file:`flaskr/flaskr` folder) and allows you to read from it.
+It is used in this example to execute a script on the database connection.
 
-The connection object provided by SQLite can give us a cursor object.
-On that cursor, there is a method to execute a complete script.  Finally, we
+The connection object provided by SQLite can give you a cursor object.
+On that cursor, there is a method to execute a complete script.  Finally, you
 only have to commit the changes.  SQLite3 and other transactional
 databases will not commit unless you explicitly tell it to.