issues: 293445250

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
293445250 MDU6SXNzdWUyOTM0NDUyNTA= 1877 TypeError for NetCDF float16 output 3169620 closed 0     4 2018-02-01T08:39:03Z 2018-02-26T10:46:47Z 2018-02-26T10:46:47Z CONTRIBUTOR      

```python ds = xr.Dataset({"test": np.arange(0, 5, dtype='float16')}) ds.to_netcdf('test.nc')

```

This fails because the float16 type doesn't exist for NetCDF files, throwing an TypeError: illegal primitive data type.

It might be nice if the xarray netCDF engine promoted this to float32 instead.

Output of xr.show_versions()

INSTALLED VERSIONS ------------------ commit: None python: 3.6.4.final.0 python-bits: 64 OS: Linux OS-release: 3.11.0-26-generic machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_GB.UTF-8 LOCALE: en_GB.UTF-8 xarray: 0.10.0 pandas: 0.22.0 numpy: 1.14.0 scipy: 1.0.0 netCDF4: 1.3.1 h5netcdf: 0.5.0 Nio: None bottleneck: 1.2.1 cyordereddict: None dask: 0.16.1 matplotlib: 2.1.2 cartopy: 0.15.1 seaborn: 0.8.1 setuptools: 38.4.0 pip: 9.0.1 conda: None pytest: None IPython: 6.2.1 sphinx: None 
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   completed 13221727 issue

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