Using "index" in a Series with a dict produces results inconsistent with documentation.
#### Code Sample, a copy-pastable example if possible

```python
# The first case shows that dicts cause the index argument to be more of a WHERE selector for rows...

>>> pd.Series({"a": 1, "b": 2, "c": 3}, index=["a", "b"])
a    1
b    2
dtype: int64

# But the docs + using a list have an error thrown if the index size does not match the length of the data.
>>> pd.Series(["a", "b", "c"], index=[0, 1])
# Error...
ValueError: Length of passed values is 3, index implies 2
```
#### Problem description

The current behavior with dicts is inconsistent with the documentation.  Moreover, there should be consistent behavior between passing a dict and passing an array into the series.

#### Expected Output


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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.3.final.0
python-bits      : 64
OS               : Darwin
OS-release       : 17.7.0
machine          : x86_64
processor        : i386
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.1
numpy            : 1.17.2
pytz             : 2019.2
dateutil         : 2.8.0
pip              : 19.1.1
setuptools       : 41.2.0
Cython           : 0.29.12
pytest           : 5.0.1
hypothesis       : None
sphinx           : 2.1.2
blosc            : None
feather          : None
xlsxwriter       : 1.1.8
lxml.etree       : 4.3.4
html5lib         : 1.0.1
pymysql          : None
psycopg2         : None
jinja2           : 2.10.1
IPython          : 7.6.1
pandas_datareader: None
bs4              : 4.7.1
bottleneck       : 1.2.1
fastparquet      : None
gcsfs            : None
lxml.etree       : 4.3.4
matplotlib       : 3.1.0
numexpr          : 2.6.9
odfpy            : None
openpyxl         : 2.6.2
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.3.0
sqlalchemy       : 1.3.8
tables           : 3.5.2
xarray           : None
xlrd             : 1.2.0
xlwt             : 1.3.0
xlsxwriter       : 1.1.8
</details>
