add unit tests for remove_from_dict

Use threading only if futures is installed.

Account:
* add appbase calls
* Parse all amounts
Asset
* Made appbase ready
* supports different asses, diffined in chains.py
Block
* add appbase calls
blockchain
* improve get_estimated_block_num
* add threaded blocks method
Comments
* add appbase calls
Discussions
* add appbase calls
Market
* add appbase calls
Steem
* current_median_history_price -> get_current_median_history
* get_reward_fund -> get_reward_funds
* get_next_scheduled_hardfork -> get_hardfork_properties
* get_hardfork_version removed
* get_reserve_ratio added
* get_witness_schedule added
Transactionbuilder
* appbase calls added
Vote
* appbase calls added
Wallet
* appbase calls added
Witness
*appbase calls added
* WitnessesByIds removed
* LookupWitnesses -> ListWitnesses
steemnoderpc
* Uses now GrapheneRPC
* appbase property added
* get_use_appbase added
* network_version added in check
Chains
* chain for appbase added
* assets restructured
* min_version added
Graphenapi removed
Graphenesrpc removed
graphenerpc added
* supports websocket and http, authomatic switching depending on the https or wss.
* Checks the blockchain_version, if 0.19.4 -> appbase ready
* Add appbase logig
* Handing for request and websocket added
Examples
* benchmark_beem is ready for appbase
* print_appbase_calls added
* print_comments added
* watching the watchers added
Unit tests fixed

flake8 test added to travis
appveyor fixed
formatTimedelta used
flake8 fix
websocket improved

Wallet contains steem instance

Tox.ini improved

Some code improvements

Unit tests fixed for STEEM-style encrypted memos

Account:
* sp vp properties added
* print_info improved
* reputation -> get_reputation
* voting_power -> get_voting_power
* steem_power -> get_steem_power
precision removed
balance -> get_balance

CLI
* set, config createwallet, walletinfo, addkey, listkeys, listaccounts and changewalletpasswordphrase added

create_account_with_delegate added

Unittests
Unit tests fixed and added

Click and prettytable added to requirements
CLI added with following commands:
* balance
* info
Unit tests for CLI added

Python2 comp
* str comp added
* py23 with py23_bytes added with unit tests
* moved back to __bytes__
* super() made compatible with python 2
Account:
* allow and disallow moved from steem
* small improvements
Comment
get_votes added
Steem
* Doku improved
Vote
* bug fixes
* printAsTable
Wallet
* getPostingKeyForAccount added
test_vote added
test_testnet added
test_py23 added