Added JsonSerializerSettings to refitSettings

Refits will now use a jsonSerializerSettings object to control how to
serialize objects.
Fixed spacing and added a readme blurb
Changed spacing, changed how a call was made.
Fixed a null reference exception

DefaultSettings is apparently null if never set.
Fixed typo in readme.
Update RefitSettings.cs

Removed dangerous initializing statement.
Update README.md
Added tests

My tests make it so the default setting is configured to CamelCase
forcing the property to be used or fail.
Merge pull request #80 from mburbea/master

Added JsonSerializerSettings to refitSettings