Setting file encoding to ascii-8bit (for ruby 2.0.0)

The explicit specification of the file encoding prepares the files for a
migration to ruby 2.0.0. It does not break support for ruby versions
prior 2.0.0.
adjust usage of mocks to changes in MiniTest
cleanup protocol/block spec
Block.from_json: check block hash and merkle root
specs for Node command/monitor API
make specs work with simplecov again
rename Builder methods to avoid name clashes
update documentation
create unsigned tx and remember sig_hash for each input

allows the wallet to create transactions spending outputs for which
we don't have the private key, so we can't sign them.
instead, remember the signature hash that needs to be signed, so
they can easily be signed later.
#create_tx and #assemble_tx commands

allows for easy creation of transactions without parsing any bitcoin-specific things
and without the need to reveal the privatekey to the node
Adding 'Compatible with...' section to README.rdoc
fix command_api_spec when SimpleCov isn't installed

  also workaround this warning:

    command_api_spec.rb:35: warning: already initialized constant RULES
require bacon 1.2.0 because 1.1.0 stopped working with new tests