Treat "(cid:%d)" as a possible char to reduce "Out of order" warnings

[HiromuHota]

Description of the problems or issues

Is your pull request related to a problem? Please describe.

Related to #33, currently pdftotree produces CID characters like (cid:176).
This is now totally expected behaviour of pdftotree, so "Out of order warning" should not be raised.

Does your pull request fix any issue.

N/A

Description of the proposed changes

Treat "(cid:%d)" as a possible char

Test plan

Test with paleo.pdf that produces "Out of order" warnings

Checklist

• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• I have updated the CHANGELOG.md accordingly.

[codecov-io]

Codecov Report

Merging #102 into master will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #102      +/-   ##
==========================================
- Coverage   66.83%   66.83%   -0.01%     
==========================================
  Files          24       24              
  Lines        2593     2596       +3     
==========================================
+ Hits         1733     1735       +2     
- Misses        860      861       +1     

Flag	Coverage Δ
#unittests	66.83% <100.00%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
pdftotree/TreeExtract.py	89.26% <100.00%> (-0.28%)	⬇️
tests/test_basic.py	96.10% <100.00%> (+0.10%)	⬆️

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