limit size of strings in TemplateErrors

[boulter]

so huge objects don't become huge strings.

[codecov-io]

Codecov Report

Merging #209 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #209      +/-   ##
============================================
+ Coverage     71.35%   71.36%   +0.01%     
- Complexity     1352     1353       +1     
============================================
  Files           215      215              
  Lines          4280     4282       +2     
  Branches        682      683       +1     
============================================
+ Hits           3054     3056       +2     
  Misses          985      985              
  Partials        241      241

Impacted Files	Coverage Δ	Complexity Δ
...a/com/hubspot/jinjava/interpret/TemplateError.java	66.91% <100%> (+0.5%)	21 <1> (+1)	⬆️

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