**Set default n value to None instead of -1** Added a threading limit based on the number of CPU's on the machine
**Set default n value to None instead of -1**
Added a threading limit based on the number of CPU's on the machine

Enabled the min_procs and max_procs class variables and changed the default
value of the n arugment

maxamillion/image-scanner,maxamillion/image-scanner,simon3z/image-scanner,simon3z/image-scanner,baude/image-scanner,baude/image-scanner,simon3z/image-scanner,maxamillion/image-scanner,baude/image-scanner