implemented inner_ext with a FunctionFunctorInterface. Modified test_inner.cc to include new test cases
Merge branch 'inner_ext_ffi'. This merge fixes inner_ext with a functor
instead of a function. It also modifies src/examples/test_inner.cc to
test this new functionality and to compare the results to inner() and
inner_ext() with an externally provided analytic function.
Merge pull request #94 from richford/master

Fix implementation of inner_ext with a FunctionFunctorInterface