Update CHANGELOG and bump version to 5.3.6 #391

Job	Run time
lint	23s
test (2.1, gems/rails3.gemfile)	20s
test (2.2)	23s
test (2.3)	26s
test (2.4)	20s
test (2.5)	20s
test (2.6)	26s
test (2.6, gems/typhoeus.gemfile, typhoeus)	26s
test (2.6, gems/octoshark.gemfile)	23s
test (2.6, gems/rails3.gemfile, 1.17.3)	25s
test (2.7)	27s
test (2.7, true)	21s
test (3.0)	9s
test (3.0, true)	13s
test (3.0, gems/instruments.gemfile, instruments)	10s
test (3.0, gems/instruments.gemfile, true, instruments)	10s
test (3.0, gems/sidekiq.gemfile, sidekiq_install)	10s
test (3.1)	12s
test (3.2)	12s
	5m 56s

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