Fix Ruby 2.7 keyword arguments warnings

[pocke]

This pull request resolves Ruby 2.7 keyword argument warnings.

The warnings are introduced since Ruby 2.7. In short, we need to keyword splat operator (**) to use a hash as keyword arguments.
details: https://www.ruby-lang.org/en/news/2019/12/12/separation-of-positional-and-keyword-arguments-in-ruby-3-0/

We can confirm the warning from this repository with the test cases.

$ bundle exec rake
# Running:

............../path/to/origami/lib/origami/filters/predictors.rb:65: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
/path/to/origami/lib/origami/filters/predictors.rb:83: warning: The called method `apply_pre_prediction' is defined here
/path/to/origami/lib/origami/filters/predictors.rb:71: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
/path/to/origami/lib/origami/filters/predictors.rb:102: warning: The called method `apply_post_prediction' is defined here
................/path/to/origami/lib/origami/string.rb:440: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
/path/to/origami/lib/origami/string.rb:377: warning: The called method `initialize' is defined here
/path/to/origami/lib/origami/string.rb:420: warning: Using the last argument as keyword parameters is deprecated; maybe ** should be added to the call
/path/to/origami/lib/origami/string.rb:377: warning: The called method `initialize' is defined here
.......................

Finished in 0.556607s, 95.2198 runs/s, 767.1480 assertions/s.

53 runs, 427 assertions, 0 failures, 0 errors, 0 skips

And this pull request fixes all of them.

[ndbroadbent]

@gdelugre Sorry to bother you, but would it be possible to merge this PR and release a new version to fix the warnings?

My company is also actively using this gem, so I would be happy to help with maintaining it if you are looking for some help

[UniqueTokens]

Related: Ruby 3.0 & origami (2.1.0): Origami::Date.now throws ArgumentError #80

[corwinstephen]

@gdelugre seems to have completely disappeared. It may be worth officially migrating to a fork of this gem

[krtschmr]

so - shall we fork?