Remove 'use experimental', it doesn't work with 5.8.

Alas, "use experimental" 0.006 added a requirement for 5.10.
Use the equivalent "use if, no warnings" statement instead.

Might be a better long term fix, but this gets Travis working
again on 5.8 and that's more important.
Merge pull request #97 from schwern/bug/experimental

Remove 'use experimental', it doesn't work with 5.8.