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

fix python2.7

reduced dependency
this allow easier pushing to conda-forge

* docu improved
* get_feed, get_blog, get_blog_entries added
* get_account_votes added
* fix timezone
Amount
* export to json and str fixed
Block
* change_block_number added
Blockchain
* get_estimated_block_num added
Comment
* dates and Amounts are now converted
* json_export adapted
* get_reblogged_by added
* delete_comment added
Storage
* 2 nodes removed from default
Utils
* timezone information added to formatTimeString
Unit tests
* more tests added for account, amount, comment, price and transaction