0.24.0 breaks records oriented to_dict with non-natural naming
#### Code Sample, a copy-pastable example if possible

```python

import pandas as pd
pd.DataFrame([{'a-1': 34087, 'b': 'blablabla', 'c': 55}]).to_dict(orient='records')  # Out: [{'_0': 34087, 'b': 'blablabla', 'c': 55}]

```
#### Problem description

The behaviour of ```to_dict(orient='records')``` has changed in version 0.24. In all previous versions the result of the above test is:
```
 [{'a-1': 34087, 'b': 'blablabla', 'c': 55}]
```
but the current result is:

```
 [{'_0': 34087, 'b': 'blablabla', 'c': 55}]
```

The keys with hyphens are renamed to "_" + number.


#### Expected Output

The same as in the previous versions of Pandas:
```
 [{'a-1': 34087, 'b': 'blablabla', 'c': 55}]
```

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

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.6.final.0
python-bits: 64
OS: Linux
OS-release: 4.4.0-36-lowlatency
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.24.0
pytest: 4.0.2
pip: 18.1
setuptools: 40.7.1
Cython: 0.29.3
numpy: 1.16.0
scipy: 0.18.1
pyarrow: None
xarray: None
IPython: 5.8.0
sphinx: None
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.7
blosc: 1.5.1
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.9
feather: None
matplotlib: 2.2.2
openpyxl: 2.5.12
xlrd: 1.2.0
xlwt: 1.3.0
xlsxwriter: 1.1.2
lxml.etree: 4.2.5
bs4: 4.5.3
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.10
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None


</details>
