use api at first

[todo]

aelf-web-wallet/app/web/js/utils/crossChain.js

Lines 166 to 171 in 55ce713

	// TODO use api at first
	// http://127.0.0.1:7000/api/cross-chain/is-ready-to-receive?
	// send=http://54.199.254.157:8000
	// &receive=http://3.112.250.87:8000
	// &main_chain_id=9992731&issue_chain_id=9992731
	// &cross_transfer_tx_id=841988ce167d5c6ae6a791c0113ef95dd57840b32275e5854a056af40eb13608

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This issue was generated by todo based on a TODO comment in 55ce713 when #56 was merged. cc @AElfProject.