Add the scaffold of an ALT alignment post-processor

[clintval]

[codecov[bot]]

Codecov Report

Merging #19 into master will decrease coverage by 1.8%. The diff coverage is 57.1%.

@@           Coverage Diff            @@
##           master     #19     +/-   ##
========================================
- Coverage    93.6%   91.7%   -1.9%     
========================================
  Files          12      13      +1     
  Lines         141     146      +5     
  Branches        2       4      +2     
========================================
+ Hits          132     134      +2     
- Misses          9      12      +3