Not installable on Windows

```
D:\Work\Coding\DevDocs\devdocs>bundle exec thor docs:download --default
(1/6) DOM Events FAILED (Errno::ENOENT: No such file or directory - gunzip)
(2/6) CSS FAILED (Errno::ENOENT: No such file or directory - gunzip)
(3/6) HTML FAILED (Errno::ENOENT: No such file or directory - gunzip)
(4/6) JavaScript FAILED (Errno::ENOENT: No such file or directory - gunzip)
(5/6) DOM FAILED (Errno::ENOENT: No such file or directory - gunzip)
(6/6) HTTP FAILED (Errno::ENOENT: No such file or directory - gunzip)
Done

D:\Work\Coding\DevDocs\devdocs>bundle exec rackup
Unable to load the EventMachine C extension; To use the pure-ruby reactor, require 'em/pure_ruby'
Traceback (most recent call last):
30: from C:/Ruby26-x64/bin/rackup:23:in `'
29: from C:/Ruby26-x64/bin/rackup:23:in `load'
28: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/bin/rackup:4:in `'
27: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/server.rb:148:in `start'
26: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/server.rb:283:in `start'
25: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/server.rb:354:in `wrapped_app'
24: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/server.rb:219:in `app'
23: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/server.rb:319:in `build_app_and_options_from_config'
22: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/builder.rb:40:in `parse_file'
21: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/builder.rb:49:in `new_from_string'
20: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/builder.rb:49:in `eval'
19: from D:/Work/Coding/DevDocs/devdocs/config.ru:in `'
18: from D:/Work/Coding/DevDocs/devdocs/config.ru:in `new'
17: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/builder.rb:55:in `initialize'
16: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rack-2.0.7/lib/rack/builder.rb:55:in `instance_eval'
15: from D:/Work/Coding/DevDocs/devdocs/config.ru:5:in `block in '
14: from D:/Work/Coding/DevDocs/devdocs/config.ru:5:in `require'
13: from D:/Work/Coding/DevDocs/devdocs/lib/app.rb:4:in `'
12: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler.rb:174:in `require'
11: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in `require'
10: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:58:in `each'
9: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in `block in require'
8: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:69:in `each'
7: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in `block (2 levels) in require'
6: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/bundler-2.1.4/lib/bundler/runtime.rb:74:in `require'
5: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/thin-1.7.2/lib/thin.rb:7:in `'
4: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/thin-1.7.2/lib/thin.rb:7:in `require'
3: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/eventmachine-1.2.7-x64-mingw32/lib/eventmachine.rb:8:in `'
2: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/eventmachine-1.2.7-x64-mingw32/lib/eventmachine.rb:8:in `require'
1: from C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/eventmachine-1.2.7-x64-mingw32/lib/rubyeventmachine.rb:2:in `'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/eventmachine-1.2.7-x64-mingw32/lib/rubyeventmachine.rb:2:in `require': cannot load such file -- 2.6/rubyeventmachine (LoadError)

D:\Work\Coding\DevDocs\devdocs>
```