Add strict & warnings to .t files

Use done_testing() and require Test::More 0.88
Add more tests for bit shift operators

Fix a bug with uint128 objects and the >>= operator. I have no idea _why_ this
was broken, or why my fix fixes it, but it seems to do so.
Add repo to META info
Remove unused variable
Really fix the >>= bug

The real problem was that the SvU128x macro was calling SvI128Y when it should
call SvU128Y
Merge pull request #1 from autarch/master

Fix the SvU128x macro that was affecting the >>= operator and maybe others.
General cheanup and more and better tests.