fix: set request() path to lowercase (#146)

Always sets request() method argument method to lower case to allow requests like:
vehicle.request("GET", "odometer")

Test Plan: use getting-started-app to test uppercase method names as arguments.

* fix: set request() path to lowercase

* Use toLowerCase instead of toLocaleLowercase

doc/.template.hbs

@@ -11,4 +11,4 @@ Smartcar Node SDK documentation.
     {{/if}}
 {{/indexChildren}}
 
-{{>main}}
+{{>main}}

lib/vehicle.js

@@ -257,7 +257,7 @@ Vehicle.prototype.request = async function(
   }
 
   const rawResponse = await new SmartcarService(options).request(
-    method,
+    method.toLowerCase(),
     path,
     {body}
   );