Bump version: 2.1.4 → 2.1.5

Bump version: 2.1.3 → 2.1.4

Bump version: 2.1.2 → 2.1.3

Bump version: 2.1.1 → 2.2.0

Bump version: 2.1.1 → 2.1.2

Bump version: 1.6.0 → 1.6.1

Changelog/PRs:
  - ethereum#423: "State snapshot module"
  - ethereum#425: "Wrap encode_hex to support changes to pyrlp 0.4.7"
  - ethereum#428: "fix memory leak in vm"
  - ethereum#431: "compile_code: raise exception when solc missing"
  - ethereum#433: "fix genesis timestamp"
  - ethereum#434: "Adjust to pysha3 breaking changes"
  - ethereum#435: "Fix solidity combinedjson"
  - ethereum#438: "Install solc from zip"
  - ethereum#439: "Shouldn't have a number equal to 2^256 in EVM"
  - ethereum#441: "Always install solidity dependencies"

Bump version: 1.5.4 → 1.6.0

Changelog:
- implement EIP150 ethereum#413 ethereum#415

Bump version: 1.5.3 → 1.5.4

Changelog:
- add option to set `SOLC_BINARY` from environment ethereum#407
- allow extra args for `solc_wrapper` ethereum#410

Bump version: 1.5.2 → 1.5.3

Changelog:
- fixes for vm tracing ethereum#395
- added cool address checksum EIP55
- added solc_wrapper compatibility for solc >= 0.4.0

Bump version: 1.5.1 → 1.5.2

Changelog:
- improve event parsing, see PR ethereum#367