add convenience functions

[nicksnyder]

part of #137

[codecov]

Codecov Report

Merging #173 into master will increase coverage by 0.09%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #173      +/-   ##
==========================================
+ Coverage   71.69%   71.79%   +0.09%     
==========================================
  Files          28       28              
  Lines        2392     2400       +8     
==========================================
+ Hits         1715     1723       +8     
  Misses        581      581              
  Partials       96       96

Impacted Files	Coverage Δ
v2/i18n/localizer.go	78.26% <100%> (+2.07%)	⬆️

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