As discussed in #197, this renames the `reqs` argument to `Site`
to `connection_options`. The old name still works but triggers a
DeprecationWarning. If you specify both we raise ValueError.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

Signed-off-by: Adam Williamson <awilliam@redhat.com>

- Move the auth anchor to be above the correct section
- Add missing anchors so all sections have them
- Add blank line above the old_login anchor and use hyphen instead of _.

This fixes the warning:

DeprecationWarning: Specifying host as a tuple is deprecated as of mwclient 0.10.0. Please use the new scheme argument instead.

Use and recommend format from RFC 7231.
Give examples for custom User-Agent strings.

Closes #49

This is what is imported at the beginning of the examples.
This could also be done by changing the import to 'import mwclient'
rather than 'from mwclient import Site'.

Neither seems more correct but I have tried to follow
what seems most intended.

>>> from mwclient import Site
>>> site = mwclient.Site('en.wikipedia.org')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'mwclient' is not defined

vs.

>>> site = Site('en.wikipedia.org')
>>> page = site.pages['Greater guinea pig']
>>> text = page.text()
>>> page.exists
True

- https is standard now, so no need to explicitly declare that
- wrap lines around 90 chars
- minor rewriting

to adher to 52b9d8b8

- Adds link to the user guide from readme
- Adds a new page to the user guide on "working with files"

Add OAuth and update docs