Update OOXML to accomodate more features

[NPDW]

Added the ability for OOXML to know if it was a successful decryption, outputting 0 if successful and 1 if not. Also added a command line argument to check for encryption on OOXML files, using the ouputs in a similar manner

[codecov-io]

Codecov Report

Merging #7 into master will decrease coverage by 0.9%.
The diff coverage is 10.71%.

@@            Coverage Diff             @@
##           master       #7      +/-   ##
==========================================
- Coverage   41.33%   40.42%   -0.91%     
==========================================
  Files           9        9              
  Lines         496      512      +16     
==========================================
+ Hits          205      207       +2     
- Misses        291      305      +14

Impacted Files	Coverage Δ
msoffcrypto/format/doc97.py	35.91% <0%> (-0.2%)	⬇️
msoffcrypto/__main__.py	0% <0%> (ø)	⬆️
msoffcrypto/format/ooxml.py	41.59% <60%> (+0.3%)	⬆️

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[nolze]

Thanks! I totally agree we need a way to check if the file encrypted or not.

I added some commits to your PR:

• In order to keep -e flag for encryption (which is to come), instead of -e, use -t for --test as in gzip command.
• Make messages meaningful rather than 0 or 1, but keep these values for exit codes.
• Print messages to stderr instead of stdout.
• Return exit code 1 if the file is not enctypted, as this program expects encrypted files by deafult.
• Implement less heuristic (I hope) method to test if OOXML file is successfully decrypted, using zipfile module.

Please tell me if anything needed is missing after my changes. I'll merge this if everything is OK.

[nolze]

Merged. Thanks again!