Test for passing in an IDictionary<string, object>
Fixes StackExchange/dapper-dot-net#152

Allows use of IDictionary<string, object> as parameter objects.
I'm assuming that the && was a mistake, and that this logic should
handle both of the types equally well.
Also allows .NET 3.5 to use the IDictionary case.
Merge pull request #179 from matwilko/idictionary-fix

Allow passing an IDictionary<string, object> as parameter object