Merge branch 'ref_slice_ops_issue51' of https://github.com/cjfuller/nmatrix into cjfuller-ref_slice_ops_issue51
Merge branch 'master' of github.com:SciRuby/nmatrix into cjfuller-ref_slice_ops_issue51
Updated iterators for Ruby 2.0 (RETURN_SIZED_ENUMERATOR macro). Supports old iterators too.