Update CHANGELOG and bump version to 5.3.6 #389

Job	Run time
lint	32s
test (2.1, gems/rails3.gemfile)	30s
test (2.2)	29s
test (2.3)	29s
test (2.4)	25s
test (2.5)	32s
test (2.6)	27s
test (2.6, gems/typhoeus.gemfile, typhoeus)	25s
test (2.6, gems/octoshark.gemfile)	31s
test (2.6, gems/rails3.gemfile, 1.17.3)	26s
test (2.7)	22s
test (2.7, true)	25s
test (3.0)	13s
test (3.0, true)	14s
test (3.0, gems/instruments.gemfile, instruments)	13s
test (3.0, gems/instruments.gemfile, true, instruments)	11s
test (3.0, gems/sidekiq.gemfile, sidekiq_install)	16s
test (3.1)	16s
test (3.2)	11s
	7m 7s

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