start autocompletion for non-command keys at the 3rd character

[mikethebeer]

[coveralls]

Coverage decreased (-0.04%) to 83.692% when pulling 6a6070a on m/3char-autocomplete into 2dec408 on master.

[codecov-io]

Codecov Report

Merging #216 into master will decrease coverage by 0.04%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master     #216      +/-   ##
==========================================
- Coverage   83.73%   83.69%   -0.05%     
==========================================
  Files          16       16              
  Lines        1998     1999       +1     
==========================================
  Hits         1673     1673              
- Misses        325      326       +1

Impacted Files	Coverage Δ
src/crate/crash/repl.py	60.9% <0%> (-0.47%)	⬇️

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