+ Added a LoadObj function that reads from a std::istream. This should allow
more generic usage and possibly make testing a little easier.
o This LoadObj accepts a function that returns a
std::unique_ptr<std::istream> for a material.
+ Modified LoadMtl to read from a std::istream to allow more generic
usage.
+ Modified test.cc to check that the changes work as expected and nothing was
broken.
Tests:
+ Compiled test.cc, checked diff of output against pre change output.
Same output where expected.
