Merge branch 'master' into reduce-refunds

specs/ChainSpec/SelectingBlockProducers.md

@@ -113,7 +113,7 @@ validator_sampler = WeightedIndex([v.stake for v in validators])
 return (validators, validator_sampler)
 ```
 
-### Algorithm for selecting block producers
+## Algorithm for selecting block producers
 
 ### Input
 
@@ -126,7 +126,7 @@ return (validators, validator_sampler)
 select_validators(MAX_NUM_BP, min_stake_fraction, validator_proposals)
 ```
 
-### Algorithm for selecting chunk producers
+## Algorithm for selecting chunk producers
 
 ### Input
 
@@ -197,7 +197,7 @@ We sample validators with probability proportional to their stake using the foll
 - `weighted_sampler: WeightedIndex`
   - Allow $O(1)$ sampling
   - This structure will be based on the
-    [WeightedIndex](https://rust-random.github.io/rand/rand/distributions/struct.WeightedIndex.html)
+    [WeightedIndex](https://docs.rs/rand/latest/rand/distributions/struct.WeightedIndex.html)
     implementation (see a description of [Vose's Alias
     Method](https://en.wikipedia.org/wiki/Alias_method) for details)