Issue293 tempfile error checks

[mikebentley15]

Fixes #293

Description:
The original intent of issue #293 was to add error checking for mkstemp() and mkdtemp(). For that, it necessitated better testing for regression. Along with this change, I did the following:

• Add gcov usage for tests/flit_src to show line coverage
• Update tinydir.h to the latest version to better handle symbolic links
• Add functions rstrip(), lstrip(), strip(), basename(), and dirname() to FLiT's source
• Use the TH_TEST() macro instead of TH_REGISTER(). The former is easier and less error-prone.
• Have test coverage on every line I can (without stubbing) for fsutil.cpp

Documentation:

• Fixed documentation at the top of test_harness.h to describe the new way of creating a test
• Document the five new functions

Tests:

• Added tests for each of the new functions
• Added tests to cover uncovered lines in fsutil.h