Build against Dropwizard 1.3.7, target Java 8

[JonMR]

I tried building against Dropwizard 1.3.7 just to see what would happen.

It looks like Guava Supplier now just proxies to java.util.function.Supplier, which doesn't exist in Java 7. That's a problem since we set our compiler source and target 1.7. Changing source and target to 1.8 fixed the problem, but I was using JDK 9 and ran into a series of runtime dependency issues. I'm guessing none of this is a problem for users. Still, passing builds for development seems important.

Maybe it's time for a general refresh.

Here's my thoughts:

1. Build against Dropwizard 1.3.7
2. Target Java 8
3. Update any massively outdated dependencies
4. Replace any resulting deprecations
5. Ensure builds using Java 9-11 work without error

This would be a new major version.

I've got a branch started with some of the changes already.

[JonMR]

Running the tests on my PR gives this warning. It's harmless in the context of our tests, but it'd be nice to fix.

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.fasterxml.jackson.module.afterburner.util.MyClassLoader (file:/(removed)/.m2/repository/com/fasterxml/jackson/module/jackson-module-afterburner/2.9.6/jackson-module-afterburner-2.9.6.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int)
WARNING: Please consider reporting this to the maintainers of com.fasterxml.jackson.module.afterburner.util.MyClassLoader
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

Some cursory googling led to these suggestions:

1. Wait for Jackson 3
2. Turn off warnings (Java 9 and up only?)
3. Set some Jackson setting I don't understand (Might be Jackson version specific?)

None of which sounds ideal.

I'd also like to take a look at JUnit 5. I'm guessing tooling and IDEs have caught up by this point where it's usable. JUnit 5 has decided to ditch Rule and RuleChain in favor of extensions, which could complicate things. 👎 While that's kind of a pain, dropwizard does provide a few extensions. Knowing all that I've created a new issue for it, #35.

Edit: there's a bunch of dependency convergence issues to fix too.