Merge pull request #3043 from imcotton/reference-check

check existence of "path" for browser execution
Fix path separator issues in tests.
Merge pull request #3045 from marchaefner/master

Fix path separator issues in tests.
Avoid variable scope collision with extensions

In #3031, an extensions variable was introduced with file-level scope
that defined the filetypes that CoffeeScript can compile. However, the
Module::load patching calls findExtension() which uses a local variable
called "extensions", which was overriding the outer level one and
causing getSourceMap() to fail.
Merge pull request #3049 from dpatti/extensions-scope

Avoid variable scope collision with extensions
parallelized script loading in browser, yet order remain
remove logic redundancy
simplify logic and changing less from before
rebuild for PR #3012