Updated abort behavior (#1141)

* Updated abort behavior

- Support for aborting a request with the promise api
- Aborting a request will cause a RequestAbortedError
- Normalized Connection class errors, now every error returned is
wrapped by the client errors constructors

* Updated test

* Updated docs

* Updated code generation script

* Renamed test

* Code coverage

* Avoid calling twice transport.request

lib/Connection.js

@@ -12,7 +12,12 @@ const debug = require('debug')('elasticsearch')
 const decompressResponse = require('decompress-response')
 const pump = require('pump')
 const INVALID_PATH_REGEX = /[^\u0021-\u00ff]/
-const { TimeoutError, ConfigurationError } = require('./errors')
+const {
+  ConnectionError,
+  RequestAbortedError,
+  TimeoutError,
+  ConfigurationError
+} = require('./errors')
 
 class Connection {
   constructor (opts = {}) {
@@ -95,7 +100,7 @@ class Connection {
       if (ended === false) {
         ended = true
         this._openRequests--
-        callback(err, null)
+        callback(new ConnectionError(err.message), null)
       }
     })
 
@@ -105,6 +110,7 @@ class Connection {
       if (ended === false) {
         ended = true
         this._openRequests--
+        callback(new RequestAbortedError(), null)
       }
     })