Added wrapAround parameter to SP 

Added wrapAround parameter to SP so the behavior of _mapPotential can be chosen by user.

Also made a relatively small change in the way _mapPotential maps inputs to columns when potentialRadius is smaller than the largest input dimension.  See images below. 

Fixes #1211
Fixes #1216
Fixes https://github.com/numenta/nupic/issues/884

@chetan51 please review
The original was using a float `1.0` for the version (really annoying) so to be safe do something like this:
```
# Original version was a float so check for anything less than 2.
if state['_version'] < 2:
```