Merge pull request #8 from ThePhD/master

Makes everything build with VC++ and also adds a void overload for `sol::function`.
Fix bug with sol::object not being copyable
Cast result of floating point retrieval before receiving it
A hefty slice of changes for functions on the proxy. Not necessary, but was fun to get around MSVC's ICE errors.
Merge remote-tracking branch 'root/master'

* root/master:
  Cast result of floating point retrieval before receiving it
  Fix bug with sol::object not being copyable