Fix truthy for numeric values

[emazv72]

Literals for number 0 are considered falsy with with patch.

Could you please review and merge commits 943b187 and 8fef46d?

[codecov]

Codecov Report

Merging #52 into master will increase coverage by 0.07%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #52      +/-   ##
=========================================
+ Coverage   99.83%   99.9%   +0.07%     
=========================================
  Files          73      57      -16     
  Lines        3054    2204     -850     
=========================================
- Hits         3049    2202     -847     
+ Misses          5       2       -3

Impacted Files	Coverage Δ
src/Stubble.Core/Contexts/Context.cs	100% <100%> (ø)	⬆️
...le.Compilation/Settings/CompilerSettingsBuilder.cs
...n/Renderers/TokenRenderers/SectionTokenRenderer.cs
...ubble.Compilation/Renderers/CompilationRenderer.cs
...c/Stubble.Compilation/Settings/CompilerSettings.cs
...n/Renderers/TokenRenderers/LiteralTokenRenderer.cs
.../Stubble.Compilation/Class/EnumerationConverter.cs
...n/Renderers/TokenRenderers/PartialTokenRenderer.cs
...ion/Renderers/PartialLambdaExpressionDefinition.cs
...rc/Stubble.Compilation/Settings/DefaultSettings.cs
... and 7 more

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[Romanx]

Thank you very much for you contribution