Add a .gemspec file.

* Metadata was copied from the evil-winrm 3.3 release:
  https://rubygems.org/gems/evil-winrm/versions/3.3
* Added `bin/evil-winrm` which simply loads/executes `evil-winrm.rb`.

bin/evil-winrm

@@ -0,0 +1,3 @@
+#!/usr/bin/env ruby
+
+require File.expand_path('../evil-winrm.rb',__dir__)

evil-winrm.gemspec

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+# frozen_string_literal: true
+
+Gem::Specification.new do |spec|
+  spec.name = "evil-winrm"
+  spec.version = '3.4'
+  spec.license = 'LGPL-3.0'
+  spec.authors = ["CyberVaca", "OscarAkaElvis", "Jarilaos", "Arale61"]
+  spec.email = ["oscar.alfonso.diaz@gmail.com"]
+
+  spec.summary = "Evil-WinRM"
+  spec.description = "The ultimate WinRM shell for hacking/pentesting"
+  spec.homepage = "https://github.com/Hackplayers/evil-winrm#readme"
+  spec.required_ruby_version = ">= 2.3"
+
+  spec.files = Dir.chdir(File.expand_path(__dir__)) do
+    `git ls-files -z`.split("\x0").reject do |f|
+      (f == __FILE__) || f.match(%r{\A(?:(?:bin|test|spec|features)/|\.(?:git|travis|circleci)|appveyor)})
+    end
+  end
+  spec.bindir = "bin"
+  spec.executables = ["evil-winrm"]
+
+  spec.add_dependency "winrm",     ">= 2.3.2"
+  spec.add_dependency "winrm-fs",  ">= 1.3.2"
+  spec.add_dependency "stringio",  ">= 0.0.2"
+  spec.add_dependency "logger",    ">= 1.4.3"
+  spec.add_dependency "fileutils", ">= 0.7.2"
+
+  spec.post_install_message = "Happy hacking! :)"
+end