🏗 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/yaml_util.py

@@ -1,7 +1,6 @@
 from __future__ import print_function
 
 import codecs
-from collections import OrderedDict
 import fnmatch
 import logging
 import os
@@ -13,6 +12,7 @@ import yaml.constructor
 from esphome import core
 from esphome.core import EsphomeError, HexInt, IPAddress, Lambda, MACAddress, TimePeriod
 from esphome.py_compat import string_types, text_type, IS_PY2
+from esphome.util import OrderedDict
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -397,6 +397,10 @@ yaml.SafeDumper.add_representer(
 )
 
 yaml.SafeDumper.add_representer(str, unicode_representer)
+yaml.SafeDumper.add_representer(
+    core.AutoLoad,
+    lambda dumper, value: represent_odict(dumper, 'tag:yaml.org,2002:map', value)
+)
 if IS_PY2:
     yaml.SafeDumper.add_representer(unicode, unicode_representer)
 yaml.SafeDumper.add_representer(HexInt, hex_int_representer)