Move installation guide out of README.

    $ [sudo] gem install jsduck

If you encounter errors during gem installation, you may need to

install the header files for compiling extension modules for Ruby 1.9.

For Debian systems you'll need the `ruby1.9-dev` package.  For Red Hat

/ CentOS / Fedora use the `ruby-devel` package.

In **OSX Mountain Lion** the compilation of `therubyracer` dependency

often fails for so far unknown reasons.  Most users have found a

solution in upgrading to Ruby 1.9 using [RVM][].

For **Windows** users out there, you can download the binary version,

which includes Ruby interpreter and all dependencies bundled in a

single .exe file.  Grab it from the [download page][].

Alternatively you can install through rubygems, but you need to do

some additional tweaks. First go and [download][libs download]

therubyracer gem and v8 lib that stereobooster has built for

windows. You need to install this special rubyracer version instead of

the one from rubygems:

    > gem install therubyracer-0.11.0beta1-x86-mingw32.gem

To make it actually work you need `v8.dll` somewhere in your

system. Extract the `lib_v8.3.11.9.zip` take the `v8.dll` inside it

and place into the `bin` directory of your Ruby installation (other

dirs that are on your PATH can work too, but I've found this to be the

most sensible place to put it). Now you're ready to install JSDuck:

    > gem install jsduck

[RVM]: https://rvm.io/

[download page]: https://sourceforge.net/projects/jsduck/files/

[libs download]: https://github.com/stereobooster/therubyracer/downloads

Windows users probably want to [download a binary release][winbin].

See the [installation guide][] for help when you run into problems.

[winbin]: https://sourceforge.net/projects/jsduck/files/

[installation guide]: https://github.com/senchalabs/jsduck/wiki/Installation

Usage

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