Added global headers option

index.js

@@ -50,6 +50,7 @@ class Client extends EventEmitter {
       compression: false,
       ssl: null,
       agent: null,
+      headers: {},
       nodeFilter: null,
       nodeWeighter: null,
       nodeSelector: 'round-robin'
@@ -85,7 +86,8 @@ class Client extends EventEmitter {
       sniffOnConnectionFault: options.sniffOnConnectionFault,
       sniffEndpoint: options.sniffEndpoint,
       suggestCompression: options.suggestCompression,
-      compression: options.compression
+      compression: options.compression,
+      headers: options.headers
     })
 
     const apis = buildApi({

lib/Transport.js

@@ -27,6 +27,7 @@ class Transport {
     this.requestTimeout = toMs(opts.requestTimeout)
     this.suggestCompression = opts.suggestCompression === true
     this.compression = opts.compression || false
+    this.headers = opts.headers || {}
     this.sniffInterval = opts.sniffInterval
     this.sniffOnConnectionFault = opts.sniffOnConnectionFault
     this.sniffEndpoint = opts.sniffEndpoint
@@ -82,7 +83,8 @@ class Transport {
         return callback(new NoLivingConnectionsError('There are not living connections'), result)
       }
 
-      const headers = options.headers || {}
+      // TODO: make this assignment FAST
+      const headers = Object.assign({}, this.headers, options.headers)
 
       // handle json body
       if (params.body != null) {