Implemented a queue to solve severe memory leaks issue
The task was not well suited for many files because it instantly spawned as many subprocesses as there were files. This changes introduces a concurrent parameter that only allows a certain number of subprocesses to be run concurrently.
Increased the default concurrence
Fixed JSHint error
Made error message more descriptive in non verbose mode
Merge pull request #11 from LaurentGoderre/fix-memory-leaks

Implemented a queue to solve severe memory leaks issue