Make diffing stack safe

[mrdziuban]

Fixes #14

• Adds minimal version of cats.Eval which guarantees stack safety when using map/flatMap
• Updates all methods in XmlDiffComputer to wrap their results in Eval
• Sets the JVM stack size when running tests to 256K and adds a test to verify that diffing elements with a lot of children does not throw a StackOverflowError

[mrdziuban]

@andyglow is there any chance you could review this and potentially release a new version if/when it's merged? Let me know if there's any more info or clarification I can provide

[andyglow]

No, no questions..
This looks great. Thank you for your contribution.
Except... May I ask you to hide Eval machinery making it a package private?

[mrdziuban]

Sure thing @andyglow, just pushed another commit to add private[diff]

[andyglow]

lgtm

[andyglow]

hey @mrdziuban
3.0.1 has been published to sonatype
should be available in maven central soon

[mrdziuban]

Thank you!