Expand the documentation for get_connection

[Drauda1]

The field expansion feature of GraphAPI can be efficiently used through the 'fields' parameter of the get_connections method. This means that the user can obtain info from both the referenced edge in 'connection_name', and the node that is connected to 'object_id' through said edge. Doing so is very useful, as it can reduce the amount of calls to the API, and help the user access richer data through a simpler query. This information is not intuitively acquired from either the Facebook SDK for Python docs, or the GraphAPI reference guide.

[martey]

I think that this pull request is useful and that it makes the documentation clearer. The only changes I would request would be a hyperlink to the specific part of the Graph API documentation that explains field expansion, and fixing the seven errors that doc8 found:

docs/api.rst:174: D002 Trailing whitespace
docs/api.rst:175: D002 Trailing whitespace
docs/api.rst:176: D002 Trailing whitespace
docs/api.rst:177: D002 Trailing whitespace
docs/api.rst:189: D002 Trailing whitespace
docs/api.rst:174: D001 Line too long
docs/api.rst:178: D001 Line too long

[martey]

I think a link to the specific section of the Graph API documentation would be useful here.

[Drauda1]

Marty, I completely forgot about this simple request you had. Out of the blue my GitHub account popped in my mind and I have requested a pull with the changes you asked for. Thank you for this super useful SDK!

[martey]

Can you rebase your commits so that they use the latest master commit as a base? rebase -p master should do the trick.

This should allow the automated tests to run successfully.