Unhardcode node prefix & possible SCRYPT_MEMORY fix?

[FIXED]     Unhardcoded path to global node_modules.
[ADDED]     Instructions on how to install traceur (it needs to be 0.0.33, otherwise --sourcemap doesn't exist).
[FIXED]     SCRYPT_MEMORY claims the default is 32 MiB but it tries to allocate 1GiB?