Merge pull request #3 from ValeevGroup/master

sync with VG::TA::Master
Merge pull request #5 from ValeevGroup/master

sync with ValeevGroup:master
Fixed minor mistakes/typos.
Outline of how to allow nonintrusive customization of Tensor types (e.g. TWG::Tensor) for use as tiles in TA.
user must overload several free TiledArray::math::functions for their Tile type. Not clear yet how to best document this. Probably wiki.
Completed nonintrusive API for Tensor. Wiki updates are separate
Merge pull request #10 from evaleev/master

Commit pull request for non-instrusive tile interface.