Use smart_open package

[sethaxen]

This PR moves away from using the (hackish) smart_open function in python_utilities to the well-tested smart_open.open function in the smart_open package.

Fixes #57 and #47

[codecov-commenter]

Codecov Report

Merging #63 (88085e4) into master (442f511) will increase coverage by 0.01%.
The diff coverage is 62.50%.

@@            Coverage Diff             @@
##           master      #63      +/-   ##
==========================================
+ Coverage   57.18%   57.20%   +0.01%     
==========================================
  Files          18       18              
  Lines        2747     2748       +1     
  Branches      539      539              
==========================================
+ Hits         1571     1572       +1     
  Misses       1060     1060              
  Partials      116      116              

Impacted Files	Coverage Δ
e3fp/fingerprint/fprint.py	54.78% <33.33%> (ø)
e3fp/fingerprint/structs.py	71.42% <50.00%> (ø)
e3fp/conformer/util.py	43.69% <57.14%> (+0.23%)	⬆️
e3fp/fingerprint/db.py	76.53% <100.00%> (ø)

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