Tuple item leading zeroes #470

[andy-ow]

What was wrong?

issue #470
Leading zeros in tuple indexes should not be allowed.

How was it fixed?

Check for leading zeros in tuple indexes (like item00 or item001). Small change in expressions.rs + tests.

To-Do

• OPTIONAL: Update Spec if applicable

• Add entry to the release notes (may forgo for trivial changes)

• Clean up commit history

[sbillig]

@andy-ow Looks great, thanks! Could you add a simple newsfragments/510.bugfix.md describing what was fixed? (Add a trailing newline on that file, or the lint check will reject it, btw)

There's also a minor conflict with the master branch now that I've merged #509. Would you mind rebasing?

[sbillig]

@andy-ow I handled the chores I mentioned above; you weren't taking too long, I'd just like to get this PR merged in prior to #468, which would have caused a lot more merge conflicts