Add Stepper Motor Support (#206)

* Add stepper support

* Fix output set_level

* Lint

esphomeyaml/components/stepper/a4988.py

@@ -0,0 +1,35 @@
+import voluptuous as vol
+
+from esphomeyaml import pins
+from esphomeyaml.components import stepper
+import esphomeyaml.config_validation as cv
+from esphomeyaml.const import CONF_DIR_PIN, CONF_ID, CONF_SLEEP_PIN, CONF_STEP_PIN
+from esphomeyaml.helpers import App, Pvariable, add, gpio_output_pin_expression
+
+A4988 = stepper.stepper_ns.A4988
+
+PLATFORM_SCHEMA = stepper.STEPPER_PLATFORM_SCHEMA.extend({
+    vol.Required(CONF_ID): cv.declare_variable_id(A4988),
+    vol.Required(CONF_STEP_PIN): pins.gpio_output_pin_schema,
+    vol.Required(CONF_DIR_PIN): pins.gpio_output_pin_schema,
+    vol.Optional(CONF_SLEEP_PIN): pins.gpio_output_pin_schema,
+})
+
+
+def to_code(config):
+    for step_pin in gpio_output_pin_expression(config[CONF_STEP_PIN]):
+        yield
+    for dir_pin in gpio_output_pin_expression(config[CONF_DIR_PIN]):
+        yield
+    rhs = App.make_a4988(step_pin, dir_pin)
+    a4988 = Pvariable(config[CONF_ID], rhs)
+
+    if CONF_SLEEP_PIN in config:
+        for sleep_pin in gpio_output_pin_expression(config[CONF_SLEEP_PIN]):
+            yield
+        add(a4988.set_sleep_pin(sleep_pin))
+
+    stepper.setup_stepper(a4988, config)
+
+
+BUILD_FLAGS = '-DUSE_A4988'