Use 'sinon' for fake timers in tests #1512

Job	Run time
general-tests	1m 55s
dependency-review	5s
circuits-test	34m 39s
eslint-check	2m 31s
ganache-erc20-test	37m 58s
client-authentication-test	22m 24s
ganache-erc721-test	30m 53s
ganache-protocol-test	28m 50s
administrator-test	24m 10s
ganache-erc1155-test	27m 17s
adversary-test	54m 38s
ganache-tokenisation-l2-test	28m 59s
optimist-sync-test	31m 5s
periodic-payment-test	33m 0s
ping-pong-test	39m 44s
check apps for liveliness	22m 19s
check gas transactions per block	39m 10s
unit-tests	36m 14s
x509-test	35m 57s
unit-test-circuits	7m 31s
	8h 59m 19s

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