Merge pull request #33 from pjohnmeyer/addingWhatToCheckMessages

Add .what() to check messages for unhandled std::exceptions.

Adds a `UT_CATCH(std::exception...)` block to:

    CHECK
    CHECK_EQUAL
    CHECK_CLOSE
    CHECK_ARRAY_CLOSE
    CHECK_ARRAY_EQUAL
    CHECK_ARRAY2D_CLOSE

Closes #11.