Update trollop requirement from ~> 1.16 to ~> 2.9

[dependabot-preview]

Updates the requirements on trollop to permit the latest version.

Changelog

Sourced from trollop's changelog.

== [3.0.0] / 2018-08-24

• The gem has been officially renamed to optimist

== [2.1.3] / 2018-07-05

• Refactor each option type into subclasses of Option. Define a registry for the registration of each option. This makes the code more modular and facilitates extension by allowing additional Option subclasses. (thanks @​clxy)
• Fixed implementation of ignore_invalid_options. (thanks @​metcalf)
• Various warning cleanup for ruby 2.1, 2.3, etc. (thanks @​nanobowers)
• Optimist.die can now accept an error code.
• fixed default (thanks @​nanobowers)
• Change from ruby license to MIT license in the code.

== [2.1.2] / 2015-03-10

• loosen mime-types requirements (for better ruby 1.8.7 support)
• use io/console gem instead of curses (for better jruby support)
• fix parsing bug when chronic gem is not available
• allow default array to be empty if a type is specified
• better specified license and better spec coverage

== [2.1.1] / 2015-01-03

• Remove curses as a hard dependency. It is optional. This can leverage the gem if it is present.
• Fix ruby -w warnings

== 2.1.0 / 2015-01-02

• Integer parser now supports underscore separator.
• Add Parser#usage and Parser#synopsis commands for creating a standard banner
  message. Using Parser#banner directly will override both of those.
• Add Parser#ignore_invalid_options to prevent erroring on unknown options.
• Allow flags to act as switches if they have defaults set and no value is
  passed on the commandline
• Parser#opt learned to accept a block or a :callback option which it will call
  after parsing the option.
• Add Optimist::educate which displays the help message and dies.
• Reformat help message to be more GNUish.
• Fix command name in help message when script has no extension.
• Fix handling of newlines inside descriptions
• Documentation and other fixes.

== 2.0 / 2012-08-11

• Change flag logic: --no-X will always be false, and --X will always be true,
  regardless of default.
• For flags that default to true, display --no-X instead of --X in the help
  menu. Accept both versions on the commandline.
• Fix a spurious warning
• Update Rakefile to 1.9
• Minor documentation fixes

Commits

• 0046eb5 Release v2.9.9 deprecating trollop gem
• 2be726f fix ruby version
• 35b087f link changelog in gemspec
• 19dc9ab supported ruby implementations
• e7ea15a added history attribution
• 3529154 Merge pull request #98 from nanobowers/master
• 46c69af updated history since last 2.1.2 release
• d53444f Fixnum deprecated in Ruby 2.4.0
• 06a2030 tests for empty argument default tests
• 837f6a3 Check it first before parsing parameter
• Additional commits viewable in compare view

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