def initialize(gem, options={})
    require 'fileutils'

    @gem = gem
    @options = options
    process_options

    if options[:user_install] and not options[:unpack] then
      @gem_home = Gem.user_dir
      check_that_user_bin_dir_is_in_path
    end
  end
#
Constructs an Installer instance that will install the gem located at
+gem+.  +options+ is a Hash with the following keys:

:env_shebang:: Use /usr/bin/env in bin wrappers.
:force:: Overrides all version checks and security policy checks, except
for a signed-gems-only policy.
:ignore_dependencies:: Don't raise if a dependency is missing.
:install_dir:: The directory to install the gem into.
:format_executable:: Format the executable the same as the ruby executable.
If your ruby is ruby18, foo_exec will be installed as
foo_exec18.
:security_policy:: Use the specified security policy.  See Gem::Security
:wrappers:: Install wrappers if true, symlinks if false.