added Bitset class.. represents a bitfield ala std::bitset in C++
add comparison __eq__ operator to Bitset class.
prefix queryable BitTree class.
multiple values for leaves in bittree
bugfix: bittree lookup branch if not find branch
Merge remote-tracking branch 'upstream/master'
* Fix requerimentes missing
* method for select the network by monkeypatching
new example fetch_block_header