Correct gem version number in README.rdoc
fix exception getting script address from invalid transactions (see testnet aba0441c4c9933dcd7db789c39053739ec435ab742ed2c23c05f22f1488c0bfd)
validation: pass block validator reference to individual tx validators

This way the tx validator can still use the optimizations provided by fetching all
data at once in the block validator, but it is only done when actually needed.
Without this it would always fetch the data even when it's just doing a syntax validation,
i.e. when storing blocks before the last checkpoint.
storage: ignore OP_RETURN scripts explicitly so they don't log an "Unknown script type" message
Merge branch 'master' of https://github.com/lian/bitcoin-ruby