Timeframes that don't evenly subdivide one day.
I'm trying to resample a dataframe from 5min to 70min timeframe where the first data point in a day would start on midnight.

Here's a better example: I want to resample daily data to weekly timeframe but with every week starting on the first day of the month so this month the first weekly data point would go from 1. June (Friday, not Monday) to 3. June (Sunday), then 4. June - 10. June. Is that possible?

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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
INSTALLED VERSIONS
------------------
commit: None

pandas: 0.23.0
pytest: None
pip: 10.0.1
setuptools: 39.0.1
Cython: 0.28.3
numpy: 1.14.3
scipy: None
pyarrow: None
xarray: None
IPython: None
sphinx: None
patsy: None
dateutil: 2.7.2
pytz: 2018.4
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: None
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
