Update readme

README.md

@@ -1,38 +1,88 @@
-ifconfig.co: Simple IP address lookup service
-=============================================
+# ifconfig.co: Simple IP address lookup service
 
 A simple service for looking up your IP address. This is the code that powers
 http://ifconfig.co
 
-Basic usage
-===========
+## Usage
 
-The usual suspects
-------------------
-    $ curl ifconfig.co
-    127.0.0.1
-    $ wget -q -O - ifconfig.co
-    127.0.0.1
+Just the business, please:
 
-BSD fetch
----------
-    $ fetch -q -o - ifconfig.co
-    127.0.0.1
+```
+$ curl ifconfig.co
+127.0.0.1
+
+$ wget -qO - ifconfig.co
+127.0.0.1
+
+$ fetch -qo - ifconfig.co
+127.0.0.1
+```
+
+A specific header:
+
+```
+$ curl ifconfig.co/user-agent
+curl/7.43.0
+
+$ curl ifconfig.co/x-ifconfig-country
+Norway
+```
+
+As JSON:
+
+```
+$ curl -H 'Accept: application/json' ifconfig.co
+{
+  "x-ifconfig-ip": "127.0.0.1"
+}
+
+$ curl ifconfig.co/x-config-ip.json
+{
+  "x-ifconfig-ip": "127.0.0.1"
+}
+```
 
 Pass the appropriate flag (usually -4 and -6) to your tool to switch between
 IPv4 and IPv6 lookup.
 
-Features
-========
+The subdomain http://v4.ifconfig.co can be used to force IPv4 lookup.
+
+## Features
+
 * Easy to remember domain name
 * Supports IPv4 and IPv6
 * Open source
 * Fast
 * Supports typical CLI tools (curl, wget and fetch)
 * JSON output (optional)
+* Country lookup for IP address through the MaxMind GeoIP2 database
+
+## Why?
 
-Why?
-====
 * To scratch an itch
 * An excuse to use Go for something
 * Faster than ifconfig.me and has IPv6 support
+
+## Building
+
+Compiling requires the [Golang compiler](https://golang.org/) to be installed.
+This application can be installed by using `go get`:
+
+`go get github.com/martinp/ifconfigd`
+
+### Usage
+
+```
+ifconfigd -h
+Usage:
+  ifconfigd [OPTIONS]
+
+Application Options:
+  -f, --file=FILE      Path to GeoIP database
+  -l, --listen=ADDR    Listening address (:8080)
+  -x, --cors           Allow requests from other domains (false)
+  -t, --template=      Path to template (index.html)
+
+Help Options:
+  -h, --help           Show this help message
+```