Relicensing: Version 0.8 will be Apache 2.0 with LLVM Exception

[hsutter]

As you probably noticed, I've merged #1309. Cppfront will now have a standard commercial OSS license as of the 0.8 release which I plan to cut soon.

For PR contributors: As always, providing a contribution license agreement (CLA) is a one-time thing for each new contributor; your CLA covers all your future PRs. Because the CLA has been updated, but the basic terms are still the same, here's my plan:

• For anyone who submits a post-0.8 PR (including the PRs that already exist but aren't merged before I cut the 0.8 release), I'll ask them to provide a new CLA, even if they previously provided the old CLA for their previous PRs. Again, this is a one-time thing that will cover all future PRs.
• For anyone who submitted a past PR but isn't submitting any new ones, I don't plan to ask them to provide the new CLA. There doesn't seem to be any need for that.

Thanks again everyone for your many contributions so far!