Add mcp23008 support (#649)

* Add support for mcp23008 8-port io expander

* add-mcp23008-support

* Revert "add-mcp23008-support"

This reverts commit b4bc7785b19bf27843b140e56707b935716e3759.

* Fixed spacing typo

* removed extra space in mcp23008.cpp, line 23

* Fixed trailing whitespace issue

* Added mcp23008 component

* Added component mcp23008

* Edited typo in test/test1.ymal

Removed additional ' in line 1337

* Another typo

tests/test3.yaml

@@ -344,12 +344,19 @@ switch:
   - platform: gpio
     id: gpio_switch1
     pin:
-      mcp23017: mcp
+      mcp23017: mcp23017_hub
       number: 0
       mode: OUTPUT
-    interlock: &interlock [gpio_switch1, gpio_switch2]
+    interlock: &interlock [gpio_switch1, gpio_switch2, gpio_switch3]
   - platform: gpio
     id: gpio_switch2
+    pin:
+      mcp23008: mcp23008_hub
+      number: 0
+      mode: OUTPUT
+    interlock: *interlock
+  - platform: gpio
+    id: gpio_switch3
     pin: GPIO1
     interlock: *interlock
   - platform: custom
@@ -492,7 +499,10 @@ output:
       - id: custom_float
 
 mcp23017:
-  id: mcp
+  id: mcp23017_hub
+  
+mcp23008:
+  id: mcp23008_hub
 
 light:
   - platform: neopixelbus