Merge pull request #241 from bjorn/sequence_each

Added Sequence.each

test/core/list/each.wren

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+var words = ""
+["One", "Two", "Three"].each {|word| words = words + word }
+IO.print(words) // expect: OneTwoThree

test/core/list/each_no_items.wren

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+var i = 0
+[].each {|item| i = i + 1 }
+IO.print(i) // expect: 0

test/core/list/each_non_function_arg.wren

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+[1, 2, 3].each("string") // expect runtime error: String does not implement 'call(_)'.