Web3-klaytn

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* BugFix: ``RPCProvider`` not sending a content-type header
* Bugfix: ``web3.toWei`` now returns an integer instead of a decimal.Decimal

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* ``TestRPCProvider`` can now be imported directly from ``web3``

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* Add ``eth.admin`` interface.
* Bugfix: Format the return value of ``web3.eth.syncing``
* Bugfix: IPCProvider socket interactions are now more robust.

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* Downstream package upgrades for ``eth-testrpc`` and ``ethereum-tester-client`` to
handle configuration of the Homestead and DAO fork block numbers.

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* Rename ``web3.contract._Contract`` to ``web3.contract.Contract``
to expose it for static analysis and auto completion tools
* Allow passing string parameters to functions
* Automatically compute gas requirements for contract deployment and
* transactions.
* Contract Filters
* Block, Transaction, and Log filters
* ``web3.eth.txpool`` interface
* ``web3.eth.mining`` interface
* Fixes for encoding.

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* Bugfix to allow address types in constructor arguments.