Makes it possible to pass in basic request parameters as arrays

For example it wasn't possible to send invite requests as follows:

@graph.put_connections(1234567, "invited", :users => [1,2,3,4,5])

Instead in order to work with the API you'd need to do something
similar to:

user_ids = [1,2,3,4,5].join(',')
@graph.put_connections(1234567, "invited", :users => user_ids)
Merge branch 'bugfix/allow_arrays_as_request_param_values' of git://github.com/csaunders/koala into csaunders-bugfix/allow_arrays_as_request_param_values
Merge branch 'master' into csaunders-bugfix/allow_arrays_as_request_param_values
Simplify conditions, add test for sanitizing enumerables
Update changelog
Support string concatenation in parameter parsing for 1.8.7