Move airbrake to dedicated repo(s)

The current implementation is using an old implementation of the
Airbrake v2 api. Airbrake has release v2 since, but this package is
necessary for in-house solutions like errbit.
The number of errbit users don't justify to continue pushing this
version as the official.
That's why the official hook is now using gobrake (the official
package), and the one coming from logrus is now named "legacy".

README.md

@@ -75,17 +75,13 @@ package main
 import (
  "os"
  log "github.com/Sirupsen/logrus"
- "github.com/Sirupsen/logrus/hooks/airbrake"
+ "github.com/gemnasium/logrus-airbrake-hook"
 )
 
 func init() {
  // Log as JSON instead of the default ASCII formatter.
  log.SetFormatter(&log.JSONFormatter{})
 
- // Use the Airbrake hook to report errors that have Error severity or above to
- // an exception tracker. You can create custom hooks, see the Hooks section.
- log.AddHook(airbrake.NewHook("https://example.com", "xyz", "development"))
-
  // Output to stderr instead of stdout, could also be a file.
  log.SetOutput(os.Stderr)
 
@@ -182,13 +178,16 @@ Logrus comes with [built-in hooks](hooks/). Add those, or your custom hook, in
 ```go
 import (
  log "github.com/Sirupsen/logrus"
- "github.com/Sirupsen/logrus/hooks/airbrake"
+ "gopkg.in/gemnasium/logrus-airbrake-hook.v2" // the package is named "aibrake"
  logrus_syslog "github.com/Sirupsen/logrus/hooks/syslog"
  "log/syslog"
 )
 
 func init() {
- log.AddHook(airbrake.NewHook("https://example.com", "xyz", "development"))
+
+ // Use the Airbrake hook to report errors that have Error severity or above to
+ // an exception tracker. You can create custom hooks, see the Hooks section.
+ log.AddHook(airbrake.NewHook(123, "xyz", "production"))
 
  hook, err := logrus_syslog.NewSyslogHook("udp", "localhost:514", syslog.LOG_INFO, "")
  if err != nil {
@@ -202,7 +201,8 @@ Note: Syslog hook also support connecting to local syslog (Ex. "/dev/log" or "/v
 
 | Hook | Description |
 | ----- | ----------- |
-| [Airbrake](https://github.com/Sirupsen/logrus/blob/master/hooks/airbrake/airbrake.go) | Send errors to an exception tracking service compatible with the Airbrake API. Uses [`airbrake-go`](https://github.com/tobi/airbrake-go) behind the scenes. |
+| [Airbrake](https://github.com/gemnasium/logrus-airbrake-hook) | Send errors to the Airbrake API V3. Uses the official [`gobrake`](https://github.com/airbrake/gobrake) behind the scenes. |
+| [Airbrake "legacy"](https://github.com/gemnasium/logrus-airbrake-legacy-hook) | Send errors to an exception tracking service compatible with the Airbrake API V2. Uses [`airbrake-go`](https://github.com/tobi/airbrake-go) behind the scenes. |
 | [Papertrail](https://github.com/Sirupsen/logrus/blob/master/hooks/papertrail/papertrail.go) | Send errors to the Papertrail hosted logging service via UDP. |
 | [Syslog](https://github.com/Sirupsen/logrus/blob/master/hooks/syslog/syslog.go) | Send errors to remote syslog server. Uses standard library `log/syslog` behind the scenes. |
 | [BugSnag](https://github.com/Sirupsen/logrus/blob/master/hooks/bugsnag/bugsnag.go) | Send errors to the Bugsnag exception tracking service. |