fixed build on gcc
fixed build on gcc

strange that on linux/gcc we can use std::unique_ptr without <memory>,
but not std::make_unique.
Event stranger that on osx/clang we can use both without <memory> …

HDF-NI/hdf5.node,HDF-NI/hdf5.node,ryancole/hdf5.node,ryancole/hdf5.node,ryancole/hdf5.node,HDF-NI/hdf5.node