Minor cleanup of external begin and end NDIterator friend functions.
Added friend declaration and changed template argument to allow conversion between NDIterators with convertible iterator types.
Changed axpy to test iterator wrapper
backup for implementing gemm
Implemented generic AXPY, SCAL, GEMM. ColMajor support currently works only for dense tensor
Added alias NDConstIterator to NDIterator<Tensor, Tensor::const_iterator>
Changed conversion from NDIterator<Tensor,Tensor::iterator> to NDIterator<Tensor,Tensor::const_iterator> to use a conversion operator instead of templated constructor.
Merge pull request #2 from emstoudenmire/master

NDIterator edits
TODO: cast operator is to be replaced by much clever way to perform conversion from iterator to const_iterator
Implemented dot and gemv, it might work at least in dense tensor level...
Merged changes in NDIterator from Miles
Fixed bugs in generic dot
Merge remote-tracking branch 'naoki/master' into slice

Conflicts:
	btas/nditerator.h
Renamed tie to tieIndex in slice.h to avoid conflicts with std::tie. Changed implementation to use std::array for unpacking arguments.