Fix issues with using being added erroneously

[mrdziuban]

Fixes #30

It turned out this was only an issue on later scalafix/scalameta versions, so I had to upgrade dependencies to actually reproduce and fix it.

The commit with the actual fix is mrdziuban@c6be468.

The other changes were to address things related to the scalafix upgrade:

• Resolve deprecation warnings
• Use templ.body.children in the SemiAuto rule instead of just templ.children
  • In the old scalafix version, templ.children returned all the statements within the template, but now it just returns a List with one element -- the template's body -- so we need to look at the children of the body

EDIT:

This also fixes an issue where using is added to code that's calling a function returned by a method that takes using parameters. See example code in #31 (comment)

[hamnis]

Nice!
Looks good to me, leaving merging to @ingarabr

[mrdziuban]

There's one more bug I'm going to try to address here, where the using keyword is incorrectly added when calling a function returned by a method with using parameters.

For example, this code:

def test(using i: Int): String => String = s => s

given i: Int = 1
test("")

is rewritten to:

def test(using i: Int): String => String = s => s

given i: Int = 1
// Note the `using` keyword is added here but results in a compile error
test(using "")

[mrdziuban]

Fixed that bug and updated the PR title and description to match

[ingarabr]

Looks good to me. Thank you for updating dependencies and deprecated code. Much appreciated :)