Allow for omitting return types for typed method signatures #265

Job	Run time
Julia 1.0 - windows-latest - x64	3m 39s
Julia 1 - ubuntu-latest - x64	37s
Documentation	53s
Julia nightly - macos-latest - x64	1m 21s
Julia nightly - ubuntu-latest - x64	40s
Julia 1.0 - macos-latest - x64	2m 40s
Julia 1.0 - ubuntu-latest - x64	1m 40s
Julia 1 - windows-latest - x64	1m 6s
Julia nightly - windows-latest - x64	2m 45s
Julia 1 - macos-latest - x64	3m 17s
	18m 38s

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