Merge pull request #4 from jcelliott/master

Add support for pushing pointers by dereferencing
Merge pull request #5 from jcelliott/master

Add test for CanInterface to prevent panics
s/return nil/continue/ in pushStruct
Added mutexes for thread safety
Reorder functions
Added Close() function

- fixes #3
Broke apart TestCall()
Implement check if function exists

- #7