Strange behaviour of the precision display option
Consider the following example:

```python
import pandas as pd
s = pd.Series([840.0, 4200.0])
pd.set_option('precision', 0)
print(s)
pd.set_option('precision',2)
print(s)

```
The first print produces 84, 420, while the second one produces correctly 840.0 and 4200.0.

#### Problem description

If I understand docs correctly, the precision option should affect only the number of digits after the decimal point, not the digits before it.

#### Expected Output

First print shows 840 and 4200 (or 840.0, 4200.0).

#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.3.final.0
python-bits: 64
OS: Linux
OS-release: 4.14.8-300.fc27.x86_64
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: pl_PL.UTF-8
LOCALE: pl_PL.UTF-8

pandas: 0.22.0
pytest: 3.3.1
pip: 9.0.1
setuptools: 36.5.0
Cython: None
numpy: 1.14.2
scipy: 0.19.1
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: None
patsy: 0.4.1
dateutil: 2.7.0
pytz: 2018.3
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.1.2
openpyxl: 2.4.9
xlrd: 1.0.0
xlwt: None
xlsxwriter: 1.0.2
lxml: None
bs4: None
html5lib: 1.0.1
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
</details>
