Added the process.lock.* implementation for writing a lock file to mark
a process as a singleton.
Comment to process.tmp.dir.
Added the require.exists? method with unit tests for the built in
modules.
Added the require.load method to forcefully load a module even if it is
already loaded and the require.name.unload! method to remove a module by
name and made the method.remove command accept multiple method names to
remove.