🏗 Merge C++ into python codebase (#504)

## Description:

Move esphome-core codebase into esphome (and a bunch of other refactors). See https://github.com/esphome/feature-requests/issues/97

Yes this is a shit ton of work and no there's no way to automate it :( But it will be worth it 👍

Progress:
- Core support (file copy etc): 80%
- Base Abstractions (light, switch): ~50%
- Integrations: ~10%
- Working? Yes, (but only with ported components).

Other refactors:
- Moves all codegen related stuff into a single class: `esphome.codegen` (imported as `cg`)
- Rework coroutine syntax
- Move from `component/platform.py` to `domain/component.py` structure as with HA
- Move all defaults out of C++ and into config validation.
- Remove `make_...` helpers from Application class. Reason: Merge conflicts with every single new integration.
- Pointer Variables are stored globally instead of locally in setup(). Reason: stack size limit.

Future work:
- Rework const.py - Move all `CONF_...` into a conf class (usage `conf.UPDATE_INTERVAL` vs `CONF_UPDATE_INTERVAL`). Reason: Less convoluted import block
- Enable loading from `custom_components` folder.

**Related issue (if applicable):** https://github.com/esphome/feature-requests/issues/97

**Pull request in [esphome-docs](https://github.com/esphome/esphome-docs) with documentation (if applicable):** esphome/esphome-docs#<esphome-docs PR number goes here>

## Checklist:
  - [ ] The code change is tested and works locally.
  - [ ] Tests have been added to verify that the new code works (under `tests/` folder).

If user exposed functionality or configuration variables are added/changed:
  - [ ] Documentation added/updated in [esphomedocs](https://github.com/OttoWinter/esphomedocs).

esphome/components/tcs34725/tcs34725.h

@@ -0,0 +1,59 @@
+#pragma once
+
+#include "esphome/core/component.h"
+#include "esphome/components/sensor/sensor.h"
+#include "esphome/components/i2c/i2c.h"
+
+namespace esphome {
+namespace tcs34725 {
+
+enum TCS34725IntegrationTime {
+  TCS34725_INTEGRATION_TIME_2_4MS = 0xFF,
+  TCS34725_INTEGRATION_TIME_24MS = 0xF6,
+  TCS34725_INTEGRATION_TIME_50MS = 0xEB,
+  TCS34725_INTEGRATION_TIME_101MS = 0xD5,
+  TCS34725_INTEGRATION_TIME_154MS = 0xC0,
+  TCS34725_INTEGRATION_TIME_700MS = 0x00,
+};
+
+enum TCS34725Gain {
+  TCS34725_GAIN_1X = 0x00,
+  TCS34725_GAIN_4X = 0x01,
+  TCS34725_GAIN_16X = 0x02,
+  TCS34725_GAIN_60X = 0x03,
+};
+
+class TCS34725Component : public PollingComponent, public i2c::I2CDevice {
+ public:
+  TCS34725Component(uint32_t update_interval) : PollingComponent(update_interval) {}
+
+  void set_integration_time(TCS34725IntegrationTime integration_time);
+  void set_gain(TCS34725Gain gain);
+
+  void set_clear_sensor(sensor::Sensor *clear_sensor) { clear_sensor_ = clear_sensor; }
+  void set_red_sensor(sensor::Sensor *red_sensor) { red_sensor_ = red_sensor; }
+  void set_green_sensor(sensor::Sensor *green_sensor) { green_sensor_ = green_sensor; }
+  void set_blue_sensor(sensor::Sensor *blue_sensor) { blue_sensor_ = blue_sensor; }
+  void set_illuminance_sensor(sensor::Sensor *illuminance_sensor) { illuminance_sensor_ = illuminance_sensor; }
+  void set_color_temperature_sensor(sensor::Sensor *color_temperature_sensor) {
+    color_temperature_sensor_ = color_temperature_sensor;
+  }
+
+  void setup() override;
+  float get_setup_priority() const override;
+  void update() override;
+  void dump_config() override;
+
+ protected:
+  sensor::Sensor *clear_sensor_{nullptr};
+  sensor::Sensor *red_sensor_{nullptr};
+  sensor::Sensor *green_sensor_{nullptr};
+  sensor::Sensor *blue_sensor_{nullptr};
+  sensor::Sensor *illuminance_sensor_{nullptr};
+  sensor::Sensor *color_temperature_sensor_{nullptr};
+  TCS34725IntegrationTime integration_time_{TCS34725_INTEGRATION_TIME_2_4MS};
+  TCS34725Gain gain_{TCS34725_GAIN_1X};
+};
+
+}  // namespace tcs34725
+}  // namespace esphome