Merge pull request ethereum#6858 from ethereum/develop

Merge develop into release for 0.5.9 (2)

Merge pull request ethereum#6630 from ethereum/develop

Merge develop into release for 0.5.8

Merge pull request ethereum#6621 from ethereum/setVersion

Update project version.

Merge pull request ethereum#6381 from ethereum/develop

Merge develop into release for 0.5.7

Merge pull request ethereum#6269 from ethereum/develop

Merge develop into release for 0.5.6

Merge pull request ethereum#6188 from ethereum/develop

Release 0.5.5

Merge pull request ethereum#5975 from ethereum/develop

Release 0.5.4

Merge pull request ethereum#5836 from ethereum/develop

Merge develop into release for 0.5.3.

Merge pull request ethereum#5697 from ethereum/develop

Merge develop into release for 0.5.2

Merge pull request ethereum#5571 from ethereum/develop

Version 0.5.1