Add Python 3.8 build

[irisliucy]

The current issue #45 is caused by inconsistent keys in tabularInput with csvOutput headers. To fix this:

1. Read the existing log file
2. Update the csv Dictwriter with the new header using union

• Union of tabularInput's and csvOutput's header is used to make sure all keys from both instances are captured

3. Write the same log file with new key headers and old data. If the value of new key is missing, the cell is left blank.

The cons of this solution:

• The csv log file is read and write to update the inconsistent key headers. It may be time-consuming to handle a large number of csv log files because of the heavy I/O. To ensure the I/O is as efficient as possible, all file reading and writing is done in RAM and file is closed upon used.

A better approach can be:

• Expand the header on-the-go as a new key(s) is encountered. Write the log file with the new header exactly once.

#45
@avnishn
@zequnyu

[codecov]

Codecov Report

Merging #48 into master will decrease coverage by 0.83%.
The diff coverage is 73.33%.

@@            Coverage Diff             @@
##           master      #48      +/-   ##
==========================================
- Coverage   94.13%   93.29%   -0.84%     
==========================================
  Files           7        7              
  Lines         358      373      +15     
  Branches       58       60       +2     
==========================================
+ Hits          337      348      +11     
- Misses         12       16       +4     
  Partials        9        9              

Impacted Files	Coverage Δ
src/dowel/csv_output.py	90.56% <73.33%> (-6.81%)	⬇️

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[avnishn]

@irisliucy you need to open this pr onto your fork and then email us, as per the instructions.

[irisliucy]

@avnishn Sorry for the inconvenience. I've opened this pr to my fork repo instead. I appreciated your reminder.