Fix #4725: apply transpile option to require’d .coffee files (#4728)

* Fix #4725: apply transpile option to require’d .coffee files

* Use the current module’s options if it has any, before going searching up the tree

* Don’t mutate passed-in options object

test/compilation.coffee

@@ -166,3 +166,7 @@ test "using transpile from the Node API requires an object", ->
     CoffeeScript.compile '', transpile: yes
   catch exception
     eq exception.message, 'The transpile option must be given an object with options to pass to Babel'
+
+test "transpile option applies to imported .coffee files", ->
+  return if global.testingBrowser
+  doesNotThrow -> transpile 'run', "import { getSep } from './test/importing/transpile_import'\ngetSep()"

test/importing/transpile_import.coffee

@@ -0,0 +1,3 @@
+import path from 'path'
+
+export getSep = -> path.sep