Stata read categoricals gives ValueError: Categorical categories must be unique
I am trying to open some Stata files generated in [IPUMS International](https://international.ipums.org/international/), but I am getting a `ValueError: Categorical categories must be unique`. I opened in Stata and could not find a repeated category for the column I am trying to import. I had similar issues with other datasets from the same source, which seemed to be generated by missing values, but that does not seem to be the case here. Here's the [link to the file](https://drive.google.com/open?id=0By-h7HPv1NhVVllUUEFkc1JucGs) I am trying to read.
#### Code Sample, a copy-pastable example if possible

```
df = pd.read_stata('ipumsi_00014.dta', columns=['ethnicsn'])
```
#### Expected Output

```
df.shape = (1694761,1)
```
#### output of `pd.show_versions()`

```
commit: None
python: 2.7.9.final.0
python-bits: 64
OS: Darwin
OS-release: 13.4.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.1
nose: 1.3.7
pip: 8.1.2
setuptools: 18.2
Cython: 0.22.1
numpy: 1.11.1
scipy: 0.15.1
statsmodels: 0.6.1
xarray: None
IPython: 3.2.1
sphinx: None
patsy: 0.2.1
dateutil: 2.5.3
pytz: 2016.6.1
blosc: None
bottleneck: 0.8.0
tables: None
numexpr: 2.4
matplotlib: 1.4.3
openpyxl: 2.1.3
xlrd: 0.9.3
xlwt: 0.7.5
xlsxwriter: 0.6.4
lxml: 3.3.5
bs4: 4.3.2
html5lib: 0.999
httplib2: None
apiclient: None
sqlalchemy: 0.9.8
pymysql: None
psycopg2: 2.5.3 (dt dec pq3 ext)
jinja2: 2.7.3
boto: 2.34.0
pandas_datareader: None
```
