feat: more transducers

[erdos]

improve performance by the following changes

• use transducers where possible
• for dfs walk, find the initial node with DFS so zipper is not initialized where not needed

[codecov]

Codecov Report

Merging #110 (b587461) into master (3aefbda) will increase coverage by 0.01%.
The diff coverage is 97.29%.

@@            Coverage Diff             @@
##           master     #110      +/-   ##
==========================================
+ Coverage   93.07%   93.08%   +0.01%     
==========================================
  Files          25       25              
  Lines        1876     1894      +18     
  Branches      106      107       +1     
==========================================
+ Hits         1746     1763      +17     
  Misses         24       24              
- Partials      106      107       +1     

Impacted Files	Coverage Δ
src/stencil/merger.clj	99.08% <80.00%> (-0.92%)	⬇️
src/stencil/cleanup.clj	93.61% <100.00%> (ø)
src/stencil/infix.clj	98.34% <100.00%> (-0.01%)	⬇️
src/stencil/model.clj	96.93% <100.00%> (ø)
src/stencil/postprocess/table.clj	80.18% <100.00%> (-0.18%)	⬇️
src/stencil/util.clj	98.71% <100.00%> (+0.50%)	⬆️

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