Fixed signed/unsigned comparison warnings.  Added some documentation.
Fixed signed/unsigned comparison warnings.  Added some documentation.

IntelLabs/numba,stuartarchibald/numba,stuartarchibald/numba,stuartarchibald/numba,IntelLabs/numba,jriehl/numba,IntelLabs/numba,cpcloud/numba,sklam/numba,numba/numba,gmarkall/numba,jriehl/numba,cpcloud/numba,stuartarchibald/numba,gmarkall/numba,gmarkall/numba,stonebig/numba,stonebig/numba,cpcloud/numba,stonebig/numba,jriehl/numba,seibert/numba,jriehl/numba,numba/numba,numba/numba,seibert/numba,numba/numba,IntelLabs/numba,stonebig/numba,seibert/numba,IntelLabs/numba,seibert/numba,stuartarchibald/numba,cpcloud/numba,seibert/numba,jriehl/numba,sklam/numba,gmarkall/numba,stonebig/numba,numba/numba,sklam/numba,sklam/numba,sklam/numba,cpcloud/numba,gmarkall/numba