(pandas.indexes.base.Index == np.dtype('float64')) is True
#### Code Sample, a copy-pastable example if possible

I came across a weird behavior in the following code

```python
>>> import numpy as np
>>> import pandas as pd
>>> type(pd.Index(['a', 'b' , 'c'])) == np.dtype('float64')
True
```

The example can be simplified as such
```python
>>> pd.Index == np.dtype('float64')
True
```

#### Problem description

The index has a dtype of object, but it returns that it is equal to a np.dtype('float64').
It does not do this for any other dtype. 

```python
>>> x = pd.Index(['a', 'b' , 'c'])
>>> print(repr(x.dtype))
dtype('O')
>>> print(type(x))
<class 'pandas.indexes.base.Index'>
>>> print(repr(np.dtype('float64')))
dtype('float64')
```

And this is not true for any other dtype or basic numpy type
```python
>>> pd.Index == np.dtype('float128')
False
>>> pd.Index == np.dtype('int32')
False
>>> pd.Index == np.dtype('float32')
False
>>> # This is also false, it is only equal to a numpy dtype(), not a basic numpy type
>>> pd.Index == np.float64
False
```

The type of a pd.Index object returns that it is equal to a np.dtype('float64'). 
This seems like a side effect of how the pd.Index object is defined. 

Perhaps this is a bug that should be fixed?

#### Expected Output

<details>
# Paste the output here pd.show_versions() here
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Linux
OS-release: 4.4.0-75-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.19.2
nose: 1.3.7
pip: 9.0.1
setuptools: 34.1.1
Cython: 0.25.2
numpy: 1.12.1
scipy: 0.18.1
statsmodels: 0.8.0
xarray: None
IPython: 5.2.2
sphinx: None
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: 2.0.2
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.5.3
html5lib: 0.999999999
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.5
boto: 2.45.0
pandas_datareader: None
</details>
