install platform this way

.travis.yml

@@ -13,6 +13,7 @@ install:
 - pip install -U platformio
 - platformio lib install
 - platformio upgrade && platformio update
+- platformio platform install 'https://github.com/platformio/platform-espressif8266.git#feature/stage'
 - cd web && npm install && cd ..
 script:
 - platformio run -v

platformio.ini

@@ -10,7 +10,7 @@
 
 [common]
 framework = arduino
-platform = https://github.com/platformio/platform-espressif8266.git#feature/stage
+platform = espressif8266_stage
 board_f_cpu = 160000000L
 lib_deps_builtin =
   SPI