Merge pull request #300 from bocoup/modules-early-errors

CONTRIBUTING.md

test/language/import/dup-bound-names.js

test/language/module-code/dup-export-decl.js

test/language/module-code/dup-export-dflt.js

test/language/module-code/dup-export-id-as.js

test/language/module-code/dup-export-id.js

test/language/module-code/dup-lables.js

test/language/module-code/dup-lex.js

test/language/module-code/export-unresolvable.js

test/language/module-code/import-as-stmt-list-item.js

test/language/module-code/lex-and-var.js

test/language/module-code/new-target.js

test/language/module-code/super.js

test/language/module-code/undef-break.js

test/language/module-code/undef-continue.js