Fix #1322: Add note in docs about None not being sent as data

In the case:

  payload = {'key1': 'value1', 'key2': 'value2', 'key3': None}
  r = requests.get("http://httpbin.org", params=payload)

the parameter `key3` will not be sent as a parameter in the URL.

Mention this in the documentation.
Merge pull request #1464 from dpursehouse/document-none-not-sent

Fix #1322: Add note in docs about None not being sent as data
Improve documentation of netrc authentication

The documentation does not make it clear that when the credentials
from netrc are used, Requests authenticates with HTTP Basic Auth.

I just spent ages trying to figure out why it wasn't working, and
it was because although the credentials in the netrc were correct,
the server actually required HTTP Digest Auth.

Add a section in the authentication documentation to make it clear
that HTTP Basic Auth is used.
fix doc
merge
Merge pull request #1466 from s7v7nislands/fix_doc

Fix doc
Remove charset from JSON types: not valid.
Move netrc authentication documentation under the Basic Auth section
Merge pull request #1465 from dpursehouse/doc-netrc-authentication

Improve documentation of netrc authentication
Merge pull request #1470 from Lukasa/carset

Remove charset from JSON types: not valid.
Some cosmetic updates to the docs

Signed-off-by: Kwpolska <kwpolska@gmail.com>
Grammar fixes and such

Signed-off-by: Kwpolska <kwpolska@gmail.com>
fixed underline

Signed-off-by: Kwpolska <kwpolska@gmail.com>
session object should be uppercase

Signed-off-by: Kwpolska <kwpolska@gmail.com>
further treatment

Signed-off-by: Kwpolska <kwpolska@gmail.com>
Merge pull request #1474 from Kwpolska/docfix

Some tiny fixes to the documentation
Add copy method to PreparedRequest objects
Wrap long lines in the authentication documentation
Add a simple example of custom authentication in the documentation

Refs #1471
Merge pull request #1477 from dpursehouse/other-auth-basic-example

Add a simple example of custom authentication in the documentation