fix v-t pluralisation when choice is 0

[mikejacoutot]

the directive was displaying the entire string instead of the correct pluralisation

[codecov-io]

Codecov Report

Merging #882 into v8.x will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             v8.x     #882      +/-   ##
==========================================
- Coverage   96.38%   96.38%   -0.01%     
==========================================
  Files          10       10              
  Lines         886      885       -1     
==========================================
- Hits          854      853       -1     
  Misses         32       32              

Impacted Files	Coverage Δ
src/components/interpolation.js	100.00% <ø> (ø)
src/components/number.js	100.00% <ø> (ø)
src/directive.js	92.98% <ø> (ø)
src/mixin.js	94.73% <ø> (-0.07%)	⬇️

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[exoego]

Thanks !!
Could you consider to add test case(s) for this behavior ?