Support timezone conversions in datetimeformat filter.

[mattcoley]

Addresses #239

Allows you to add an optional variable to the datetimeformat filter to specify which timezone the result should be converted to. For example, |datetimeformat("%B %d, %Y, at %I:%M %p", "America/New_York") will output the time in EST instead of UTC. If no timezone is given, it will default to UTC like before. If the timezone is not valid, it will throw an InvalidDateFormatException

[codecov-io]

Codecov Report

Merging #241 into master will increase coverage by 0.22%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #241      +/-   ##
============================================
+ Coverage     71.64%   71.86%   +0.22%     
- Complexity     1380     1387       +7     
============================================
  Files           219      219              
  Lines          4338     4358      +20     
  Branches        683      687       +4     
============================================
+ Hits           3108     3132      +24     
+ Misses          996      992       -4     
  Partials        234      234

Impacted Files	Coverage Δ	Complexity Δ
...ain/java/com/hubspot/jinjava/lib/fn/Functions.java	81.9% <100%> (+2.78%)	31 <6> (+3)	⬆️
...bspot/jinjava/lib/filter/DateTimeFormatFilter.java	100% <100%> (ø)	4 <0> (ø)	⬇️
...n/java/com/hubspot/jinjava/lib/tag/TagLibrary.java	82.35% <0%> (+0.53%)	8% <0%> (+3%)	⬆️
...ubspot/jinjava/objects/date/StrftimeFormatter.java	89.47% <0%> (+2.63%)	19% <0%> (ø)	⬇️
...njava/objects/date/InvalidDateFormatException.java	75% <0%> (+75%)	1% <0%> (+1%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 00919cb...dc28adb. Read the comment docs.