solve #306, and bin in $PATH make sense now

solve #306, and bin in $PATH make sense now  #196
Almost revert #173 which lead to the bug in #306

Also remove deprecated `customFds` option in spawn
Binary might not be called "node". For example, on ubuntu it's sometimes called "nodejs", and on windows it might be renamed too because of the conflict with node.exe service from microsoft.

You can use `spawn(process.execPath, args, ...)` like it was suggested in one of the previous PRs. Or fork. Same thing.