Round-tripping with hsload and hsget

@jreadey, you used `hsload` to put our Hurricane Sandy netcdf4 file on HSDS:
```
(IOOS) rsignell@0e6be50c3dc2:~$ hsls /home/john/sandy.nc/

john domain 2017-09-07 22:11:07 /home/john/sandy.nc
1 items
```
If I try to use `hsget` to get that dataset back, I get errors:
```
(IOOS) rsignell@0e6be50c3dc2:~$ hsget /home/john/sandy.nc sandy.nc
2017-10-14 14:00:39,424 ERROR: failed to create dataset: Scalar datasets don't support chunk/filter options
ERROR: failed to create dataset: Scalar datasets don't support chunk/filter options
2017-10-14 14:01:50,324 ERROR: failed to create dataset: Scalar datasets don't support chunk/filter options
```
And although I do end up with a `sandy.nc` file, if I try to ncdump it, it doesn't work (see below). I guess that is not too surprising in light of #32, right?

But do you think one day we will be able to round-trip a dataset using `hsload` and `hsget`?
```

(IOOS) rsignell@0e6be50c3dc2:~$ ncdump -h sandy.nc
HDF5-DIAG: Error detected in HDF5 (1.8.18) thread 140414440146688:
#000: H5L.c line 1183 in H5Literate(): link iteration failed
major: Symbol table
minor: Iteration failed
#001: H5Gint.c line 844 in H5G_iterate(): error iterating over links
major: Symbol table
minor: Iteration failed
#002: H5Gobj.c line 708 in H5G__obj_iterate(): can't iterate over symbol table
major: Symbol table
minor: Iteration failed
#003: H5Gstab.c line 566 in H5G__stab_iterate(): iteration operator failed
major: Symbol table
minor: Can't move to next iterator location
#004: H5B.c line 1221 in H5B_iterate(): B-tree iteration failed
major: B-Tree node
minor: Iteration failed
#005: H5B.c line 1177 in H5B_iterate_helper(): B-tree iteration failed
major: B-Tree node
minor: Iteration failed
#006: H5Gnode.c line 1039 in H5G__node_iterate(): iteration operator failed
major: Symbol table
minor: Can't move to next iterator location
HDF5-DIAG: Error detected in HDF5 (1.8.18) thread 140414440146688:
#000: H5L.c line 1183 in H5Literate(): link iteration failed
major: Symbol table
minor: Iteration failed
#001: H5Gint.c line 844 in H5G_iterate(): error iterating over links
major: Symbol table
minor: Iteration failed
#002: H5Gobj.c line 708 in H5G__obj_iterate(): can't iterate over symbol table
major: Symbol table
minor: Iteration failed
#003: H5Gstab.c line 566 in H5G__stab_iterate(): iteration operator failed
major: Symbol table
minor: Can't move to next iterator location
#004: H5B.c line 1221 in H5B_iterate(): B-tree iteration failed
major: B-Tree node
minor: Iteration failed
#005: H5B.c line 1177 in H5B_iterate_helper(): B-tree iteration failed
major: B-Tree node
minor: Iteration failed
#006: H5Gnode.c line 1039 in H5G__node_iterate(): iteration operator failed
major: Symbol table
minor: Can't move to next iterator location
ncdump: sandy.nc: NetCDF: HDF error
(IOOS) rsignell@0e6be50c3dc2:~$
```