Merge pull request ethereum#821 from ethereum/fix-mod

fix shuffling shard mod bug

Merge pull request ethereum#755 from ethereum/dev

v0.5.0 release

Merge pull request ethereum#683 from ethereum/dev

Weekly release of dev into master

Merge pull request ethereum#683 from ethereum/dev

Weekly release of dev into master

Merge pull request ethereum#631 from ethereum/dev

Weekly release dev into master

Merge pull request ethereum#591 from ethereum/dev

Weekly release of dev into master

Merge pull request ethereum#536 from ethereum/fix_attestation_sig

Remove the repeated checks