fix comparing TxIn/Outs with objects of other classes

(it already works for blocks / txs because they only compare #hash, which every object happens to have)
postgres store: change tx.hash column type to bytea
storage: (optionally) index normalized tx hashes
fix storage config
removed cargo-cult check for input index in signature_hash_for_input
Script: accurate and not legacy signature count (no support for P2SH yet)
running specific specs using $ rake SPEC=path/to/spec
added .ruby-version to .gitignore to not mess with setup of others
sigop counts for transaction and script
basic tests for legacy_sigops_count.should
index p2sh addresses
remove duplicate #parse_script in sequel store
add support for OP_RETURN scripts

see https://github.com/bitcoin/bitcoin/pull/2738
fix tx_hash migration; only drop view if it exists
provide #as_json instead of #to_json for namecoin names
also adjust Script#get_hash160 to p2sh for namecoin
fix add_tx_nhash migration to run in specs
fix namecoin expiration calculation
optimize sequel store wrap_block
bitcoin_wallet: send to type "address" by default