Toshi json

from_json methods in tx.rb, txin.rb, txout.rb crash when parsing json responses from toshi because of the different keys used by toshi.
In particular some elements of the values_at in from_hash return nil because those are referencing keys that are there in, e.g. webbtc, but not in the toshi hash format.
I Added a from_toshi_hash method that correctly parses the toshi hash structure and extended the from_json method to try using the old hash and if it fails try the toshi hash format.