Merge pull request #13 from moteus/moteus

Add. Example of basic custom reporter.
Use TMP dir on Windows.
Improves the situation on #12. I don't know if it's enough.
I used the __gc method to try to make it delete the file on program exit,
but maybe on Windows the process is killed and the destructor metamethod
never gets a chance to run?
Merge branch 'master' of github.com:keplerproject/luacov
Change. Use `newproxy` gc method to call `on_exit` function.
Fix. Detect double calls of on_exit function.
Merge pull request #14 from moteus/onexit

Change. Use `newproxy` gc method to call `on_exit` function.
Simplify code a bit.