Feature request: More Vec methods

[niklasf]

A couple more methods from Vec would be useful. In particular:

• swap_remove()
• retain()
• truncate()

---

• impl Extend

[slightlyoutofphase]

I definitely want to add more stuff, yeah. Will take a look at these ones first.

[slightlyoutofphase]

Just pushed a commit that finishes off the list. Thanks for the request, these were definitely things I'd have needed to add at some point one way or another! Let me know if you think of anything else in the future.

[niklasf]

Awesome! Thank you very much.