Challenge 1: Write a Gemfile — Solution

# Gemfile
source "https://rubygems.org"

gem "rspec", "~> 3.12"
gem "rake"
gem "my_project_utils", path: "../my_project_utils"

=begin
Notes:
- source "https://rubygems.org" tells Bundler which registry to resolve
  gems from — required at the top of nearly every real Gemfile.
- gem "rspec", "~> 3.12" uses the pessimistic version constraint from the
  chapter: any 3.12.x patch release is acceptable, but Bundler will never
  automatically jump to 3.13 or later.
- gem "rake" with no version constraint accepts any available version,
  which is fine for a tool where breaking changes are rare and not a major
  concern for this project.
- gem "my_project_utils", path: "../my_project_utils" points Bundler at a
  local directory instead of RubyGems.org entirely — useful during
  development of a companion library that hasn't been published yet, or
  never will be (an internal-only utility gem, for example).
- Running `bundle install` against this Gemfile would generate a
  Gemfile.lock pinning exact resolved versions for rspec and rake, while
  my_project_utils is tracked by its local path instead of a version
  number.
=end