bump version
Fix Litecoin proof_of_work_limit and block reward halving
Add Dogecoin network parameter support
remove freicoin network parameters
add dogecoin helper method

  Bitcoin.dogecoin? == true if network project is set to dogecoin
Add new testnet3 seeds
Fix exception when parsing from headers only

  I was getting an argument exception because Block.new was expecting an argument: https://github.com/lian/bitcoin-ruby/blob/master/lib/bitcoin/protocol/parser.rb#L63

  This fixes the problem, but I think the API would be a bit cleaner if we could do Block.new(data, header_only: true)
Added Tx#from_toshi_hash methods to deal with new toshi hash keys
combine Tx#from_hash and Tx#from_toshi_hash
Add docs badge to README

[ci skip]