Readme for last release adapted

Blockchain
* raw_ops added to stream, when set to True stream() produces the same output as the old Blockchain.ops()
Unit tests
* Add unit tests for testing raw_ops

Account
* Parameter accuracy renamed to stop_diff
* Doku for estimate_virtual_op_num improved
* Several improvements and fixes for estimate_virtual_op_num
CLI
* rewards command improved and more paramter added
Comments
* Assure Amount class for all amounts
* is_pending improved
Doku
* tutorial about showing all posts of an account added
Unit tests
* test_account, test_cli and test_comment improved

Account
* print_info improved (Last Vote added)
* entryId changed to start_entry_id in get_feed, get_blog_entries and get_blog
*rpc.get_account_history moved to _get_account_history
* estimate_account_op added, can be used to fastly get account op numbers from dates or block nums
* history and history_reverse uses estimate_account_op
Exception
* KeyNotFound removed
Memo
* raises MissingKeyError instead of KeyNotFound
Price
* small improvement
Steem
* __repr__ added
Transactionbuilder
* get_potential_signatures, get_transaction_hex and get_required_signatures added
* raises MissingKeyError instead of KeyNotFound
VotesObject
* __contains__, __str__ and __repr__ added
Wallet
* raises MissingKeyError instead of KeyNotFound
Witness
* __contains__, __str__ and __repr__ added to WitnessObject
Steemnoderpc
* small improvements
Operationsid
* producer_reward added
Unit tests
* new function added and tests adapted to changes

Fix wallet unlock when using keyring

Account
* Improved some function, so that account works limited on GOLOS
Blockchain
* sync changes from python-bitshares
Instance
* sync changes from python-bitshares
Steem
* Improved some functions so that steem works on GOLOS
Chains
* Added GOLOS
graphenebase/Account
* derive256address_with_version added
ecsdasig
* Huge speed improvement (200%) by using cryptography
benchmark added
* benchmark for beemgraphenebase/account funcions
* benchmark for ecdsa
* benchmark for sign/verification of all transaction
Examples
* compare sign/verificaiton speed with steem
Unit tests
* use memo unittests from steem-js
* add key_format unittests from steem-js
* Improved the ecdsa tests

Account
* get_withdraw_routes added
* get_account_votes fixed for appbase
* get_vote, has_voted added
* virtual_op_count, get_curation_reward curation_stats added
* get_account_history and history_reverse added
* history improved
Blockchain
* hash_op added
CLI
* default vote weight added
* upvote added
* Info improved
Steem
* get_block_interval added
Transactionbuilder
* txbuffer.clear() added on exception
Vote
* AccountVotes fixed
GrapheneRPC
* Websocket disconnect exception handling improved
Compare_With_steem_python_account.py added
Unittests for account improved

Transactionbuild
* Automatic Signing with owner key removed
Beembase/account and beembase/bip38 removed as they are using beemgraphenebase/bip38 and beemgraphenebase/account

Amount
* fix json export
Blockchain
* improved get_estimated_block_num
Comment
* Bugfixes
Market
* Use FilledOrder for trades and recenttrades
Price
* FilledOrder fixed
* UpdateCallOrder and PriceFeed removed
Vote
* Bugfix
Unit tests
More unittests for Amount, Blockchain and comment

Wallet contains steem instance

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

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

Release of next version 0.19.5 prepared