Rails 4, custom gem with generator 'Could not find generator'

I'm building a gem simply to go through the processes, and I'm trying to add a generator to it. When I run $ rails g, my generator shows up:

Mygem:
  mygem:install

but rails doesn't recognize it

rails g mygem:install
Could not find generator mygem:install.

I have my gem pointed to the latest version in my gemfile

#mygem/lib/rails/generators/mygem_generator.rb
require 'rails/generators'
require 'rails/generators/base'

module Mygem
  class InstallGenerator < Rails::Generators::Base
    def test
        puts 'hi'
    end
  end
end

.

-mygem
  - lib
    - generators
      - mygem
        mygem_generator.rb
    - mygem
      version.rb
    mygem.rb
  - pkg
    mygem-0.0.1.gem
.gitignore
Gemfile
LICENSE.txt
README.md
Rakefile
mygem.gemspec

.

#mygem.gemspec
# coding: utf-8
lib = File.expand_path('../lib', __FILE__)
$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
require 'mygem/version'

Gem::Specification.new do |spec|
  spec.name          = "mygem"
  spec.version       = Mygem::VERSION
  spec.authors       = ["me"]
  spec.email         = ["email@email.com"]
  spec.summary       = %q{lalaala}
  spec.description   = %q{lalalalal}
  spec.homepage      = ""
  spec.license       = "MIT"

  spec.files         = `git ls-files -z`.split("\x0")
  spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
  spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
  spec.require_paths = ["lib"]

  spec.add_development_dependency "bundler", "~> 1.5"
  spec.add_development_dependency "rake"
end

We've just made a gem, and have a generator which allows you to call rails generate exception_handler:install, like this:

#lib/generators/my_gem/install_generator.rb
module MyGem
    class InstallGenerator < Rails::Generators::Base
         def test
             puts "hi"
         end
     end
end

This should help you - it works for us