relicense shootout-meteor.rs

part of #14248, fix #14420

Removed @richo's contribution (outdated comment)

Quoting @brson: let's move forward with this one. The only
statement I'm missing is @richo's and it sounds like his was a
minor patch.
Update AUTHORS.txt
auto merge of #14669 : TeXitoi/rust/relicense-shootout-meteor, r=brson

part of #14248, fix #14420

Removed @richo's contribution (outdated comment)

Quoting @brson: let's move forward with this one. The only
statement I'm missing is @richo's and it sounds like his was a
minor patch.
Fix documentation for `slice()`

Fixes https://github.com/mozilla/rust/issues/14577
Document BigInt's new and from_slice methods

Fixes https://github.com/mozilla/rust/issues/14639
Change to_str().to_string() to just to_str()
auto merge of #14667 : aochagavia/rust/pr2, r=huonw
auto merge of #14668 : aochagavia/rust/pr3, r=alexcrichton

Closes https://github.com/mozilla/rust/issues/14577
Closes https://github.com/mozilla/rust/issues/14639
auto merge of #14671 : aochagavia/rust/patch-1, r=alexcrichton