docs(README): Add local composer installation example and removed installer...

[Drupal ESLint](https://www.drupal.org/node/1955232) documentation.

## Installation

## Global installation

First, make sure Composer is installed correctly:

If you get composer not found or similar, follow Composer's installation

instructions.

Install Coder (8.x-3.x) in your global Composer directory in your home directory

(`~/.composer`):

Install Coder (8.3.x) in your global Composer directory in your home directory

(`~/.config/composer`):

    composer global require drupal/coder

To make the `phpcs` and `phpcbf` commands available globally, add the Composer

bin path to your `$PATH` variable in `~/.profile`, `~/.bashrc` or `~/.zshrc`:

    export PATH="$PATH:$HOME/.composer/vendor/bin"

### Composer Installer Plugins

The Coder package (>= 8.2.11) now works with Composer Installer Plugins,

that find and register standards whenever packages are installed or updated.

To use such a plugin within your project, follow these steps.

    composer require --dev drupal/coder

Now, you will see Drupal and DrupalPractice listed in the available PHP

CodeSniffer standards.

    vendor/bin/phpcs -i

The same can be done for a Composer global installation.

    composer global require drupal/coder

    export PATH="$PATH:$HOME/.config/composer/vendor/bin"

## Usage

    phpcbf --standard=Drupal --extensions=php,module,inc,install,test,profile,theme,css,info,txt,md,yml /file/to/drupal/example_module

## Local installation in your Drupal project

For collaborating developer teams it makes sense to lock a Coder version with

your other development dependencies locally. In your project where you have your

composer.json file execute this:

    composer require --dev drupal/coder

Then you can run Coder on your custom module code like this:

    ./vendor/bin/phpcs --standard=Drupal --extensions=php,module,inc,install,test,profile,theme,css,info,txt,md,yml web/modules/custom

To simplify execution it is highly recommended to use a settings file, see below.

## Store settings in a phpcs.xml.dist file

In order to save and commit your PHPCS settings to Git you can use a

Then you can invoke phpcs without any options and it will read phpcs.xml.dist

from the current directory. This can also be useful for Continuous Integration

setups.

setups. Example:

    ./vendor/bin/phpcs -p

## Working with Editors