Add easy testing for EVM contracts

Currently, `tester.state#contract()` allows creating contracts easily
with Serpent code. This adds a new method `tester.state#evm()` for
creating contracts in the same way with arbitrary EVM code.
Merge pull request #164 from qualiabyte/master

Add easy testing for EVM contracts
Merge remote-tracking branch 'upstream/master'
Added Sha3- and environmentalInfo- test