Requirements.txt contains packages that no longer exist on PyPI

[Tehsurfer]

To reproduce:

git clone https://github.com/nih-sparc/sparc-api.git
pip install -r requirements.txt

Which stops giving the error:

ERROR: Could not find a version that satisfies the requirement post==2019.4.13g

After a little investigation I found this comment from a PyPI admin saying that a the following packages have been removed from PyPI:

get==2019.4.13 
post==2019.4.13 
request==2019.4.13

Seems to run fine without them. I've put the following pull request in to fix this:
#24