Make compatible with python 3 (#281)

* Make compatible with python 3

* Update travis

* Env

* Fix typo

* Fix install correct platformio

* Lint

* Fix build flags

* Lint

* Upgrade pylint

* Lint

esphomeyaml/components/sensor/ads1115.py

@@ -6,6 +6,7 @@ import esphomeyaml.config_validation as cv
 from esphomeyaml.const import CONF_ADS1115_ID, CONF_GAIN, CONF_MULTIPLEXER, CONF_NAME, \
     CONF_UPDATE_INTERVAL
 from esphomeyaml.cpp_generator import get_variable
+from esphomeyaml.py_compat import string_types
 
 DEPENDENCIES = ['ads1115']
 
@@ -35,7 +36,7 @@ GAIN = {
 def validate_gain(value):
     if isinstance(value, float):
         value = u'{:0.03f}'.format(value)
-    elif not isinstance(value, (str, unicode)):
+    elif not isinstance(value, string_types):
         raise vol.Invalid('invalid gain "{}"'.format(value))
 
     return cv.one_of(*GAIN)(value)

esphomeyaml/components/sensor/pmsx003.py

@@ -36,7 +36,7 @@ SENSORS_TO_TYPE = {
 
 
 def validate_pmsx003_sensors(value):
-    for key, types in SENSORS_TO_TYPE.iteritems():
+    for key, types in SENSORS_TO_TYPE.items():
         if key in value and value[CONF_TYPE] not in types:
             raise vol.Invalid(u"{} does not have {} sensor!".format(value[CONF_TYPE], key))
     return value

esphomeyaml/components/sensor/pulse_counter.py

@@ -35,8 +35,8 @@ def validate_internal_filter(value):
         if value.total_microseconds > 13:
             raise vol.Invalid("Maximum internal filter value for ESP32 is 13us")
         return value
-    else:
-        return cv.positive_time_period_microseconds(value)
+
+    return cv.positive_time_period_microseconds(value)
 
 
 PLATFORM_SCHEMA = cv.nameable(sensor.SENSOR_PLATFORM_SCHEMA.extend({