Conflicting dependencies in balancerpool.txt

[AngelaKTE]

Error message:

"ERROR: Cannot install -r balancerpool.txt (line 42) and python-dateutil==2.8.1 because these package versions have conflicting dependencies.

The conflict is caused by:
    The user requested python-dateutil==2.8.1
    ethereum-etl 1.6.1 depends on python-dateutil==2.7.0"

---

to solve the issue, I've already tried to:
a) update balancerpool.txt to request python-dateutil>=2.7.0

caused new error message

The conflict is caused by:
    The user requested python-dateutil>=2.7.0
    ethereum-etl 1.6.1 depends on python-dateutil==2.7.0
    matplotlib 3.3.4 depends on python-dateutil>=2.1
    mythx-models 1.9.3 depends on python-dateutil==2.8.1

b) set up a new environment and installed packages from scratch, but failed.

[AngelaKTE]

also tried variants in balancerpool.txt:

python-dateutil~=2.7.0
python-dateutil

...but didn't solve the issue.

[AngelaKTE]

Solved with using updated requirements.txt
after Merged #47 into dev.

[AngelaKTE]

Proposal to avoid confusion in documentation:

rename "data/requirements.txt" to "data/datapull-requirements.txt"
to avoid confusion with "requirements.txt" in top-level repo