Remove synPermActiveInactiveDec from Temporal Pooler #42

Fix [#42](https://github.com/numenta/nupic.research/issues/42)
cc: @subutai @chetan51 
The dangerous learning rule "decrease connection between an active input and an inactive target cell" has been removed. The experiments sm_pooling_1d_test  and sm_pooling_hello_world still work.
It is dangerous because the activation is generally sparse, and many inactive cells may receive active inputs. If we decrement all these connections, we lost the initial random connections quickly.

This learning rule is originally introduced to solve the "merging problem". The problem is that initially during learning, a single static world may be represented differently depends on the start position, there is no mechanism to "merge" these representations so that we only have one representation for each learned pattern. Maybe this is not an issue for real application in a hierarchy.