Elm-Reactor can not find runElmProgram on page with JS module library (like requirejs)

[AlexErofeev]

In elm-lang/elm-make#50 was added code to move Elm object from global scope if on the page any JS module library (requirejs, for example) is present. Nonetheless elm-reactor still assumes that Elm object is present in global scope. My propose is to add additional checks to function toJavaScript in file https://github.com/elm-lang/elm-reactor/blob/master/src/backend/Compile.hs

[process-bot]

Thanks for the issue! Make sure it satisfies this checklist. My human colleagues will appreciate it!

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