Add spring-webflux compatibility to handlebars-springmvc (#642)

[shortstories]

• update spring version (3.1.1.RELEASE -> 5.0.7.RELEASE)
• add spring-webflux
• update Junit version (4.11 -> 4.12)
• add handlebar spring reactive view and view resolver
  • ReactiveHandlebarsView
  • ReactiveHandlebarsViewResolver
  • And their tests...

[codecov-io]

Codecov Report

Merging #647 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@ Coverage Diff @@## master #647 +/- ##
============================================
- Coverage 87.33% 87.28% -0.05% + Complexity 841 833 -8 
============================================
Files 78 78 Lines 3023 2989 -34 Branches 411 407 -4 ============================================
- Hits 2640 2609 -31 + Misses 261 260 -1 + Partials 122 120 -2

Impacted Files	Coverage Δ	Complexity Δ
...knack/handlebars/helper/DefaultHelperRegistry.java	74.48% <0%> (-2.15%)	20% <0%> (-2%)
...hub/jknack/handlebars/internal/FormatterChain.java	85.71% <0%> (-1.79%)	4% <0%> (-1%)
...ain/java/com/github/jknack/handlebars/Context.java	94.68% <0%> (-0.2%)	37% <0%> (ø)
...ub/jknack/handlebars/internal/TemplateBuilder.java	88.15% <0%> (-0.04%)	88% <0%> (ø)
...com/github/jknack/handlebars/internal/Partial.java	93.27% <0%> (+1.48%)	31% <0%> (-5%)	⬇️

---

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 0f45894...f142a6b. Read the comment docs.

[coveralls]

Coverage remained the same at 91.301% when pulling f142a6b on shortstories:master into 3b702a4 on jknack:master.

[jknack]

Looks good with one question.

Is Spring 5.x compatible with 3.x?

I know 3.x is old (very old) but don't want to break existing integrations

[shortstories]

I created a Spring3 test project (https://github.com/shortstories/spring3-mvc-maven-xml-hello-world) and tried to run it. It works without problems.

[nikos]

@jknack any chances this PR could be revitalized, so that Spring Webflux with Handlebars becomes available?

[codecov-commenter]

Codecov Report

Merging #647 into master will not change coverage.
The diff coverage is n/a.

@@ Coverage Diff @@## master #647 +/- ##
=========================================
Coverage 87.28% 87.28% Complexity 833 833 =========================================
Files 78 78 Lines 2989 2989 Branches 407 407 =========================================
Hits 2609 2609 Misses 260 260 Partials 120 120 

---

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 3b702a4...f142a6b. Read the comment docs.

[IRuzhnikov]

HI! how i can help for push it to master? Because it's really actual for me)