Add Captive Portal (#624)

* WIP: Captive Portal

* Updates

* Updates

* Lint

* Fixes

esphome/components/captive_portal/__init__.py

@@ -0,0 +1,26 @@
+import esphome.codegen as cg
+import esphome.config_validation as cv
+from esphome.components import web_server_base
+from esphome.components.web_server_base import CONF_WEB_SERVER_BASE_ID
+from esphome.const import CONF_ID
+from esphome.core import coroutine_with_priority
+
+AUTO_LOAD = ['web_server_base']
+DEPENDENCIES = ['wifi']
+
+captive_portal_ns = cg.esphome_ns.namespace('captive_portal')
+CaptivePortal = captive_portal_ns.class_('CaptivePortal', cg.Component)
+
+CONFIG_SCHEMA = cv.Schema({
+    cv.GenerateID(): cv.declare_id(CaptivePortal),
+    cv.GenerateID(CONF_WEB_SERVER_BASE_ID): cv.use_id(web_server_base.WebServerBase),
+}).extend(cv.COMPONENT_SCHEMA)
+
+
+@coroutine_with_priority(64.0)
+def to_code(config):
+    paren = yield cg.get_variable(config[CONF_WEB_SERVER_BASE_ID])
+
+    var = cg.new_Pvariable(config[CONF_ID], paren)
+    yield cg.register_component(var, config)
+    cg.add_define('USE_CAPTIVE_PORTAL')