Ship call logs to the user as text/plain instead of JSON (#615)

* Ship call logs to the user as text/plain instead of JSON

* Fixing swagger doc

* c.String instead of c.JSON

* Make Logs API backward compatible

* Loop over accepted MIME types

* Bump swagger API version

* Fix client build script

 previous version was producing the following "couldn't find a swagger spec"

* Logs API regression test

* Write response body without buffering

* Switch JSON and text/plain cases

* Handle Accepted content types properly

* More solid response content type handling

* Write HTTP 406 with corresponding error body

* Remove unused import

* Use handleErrorResponse

docs/swagger.yml

@@ -2,7 +2,7 @@ swagger: '2.0'
 info:
   title: fn
   description: The open source serverless platform.
-  version: "0.2.2"
+  version: "0.2.3"
 # the domain of the service
 host: "127.0.0.1:8080"
 # array of all schemes that your API supports
@@ -371,6 +371,7 @@ paths:
       tags:
         - Call
         - Log
+      produces: ['text/plain',]
       parameters:
         - name: app
           description: App Name
@@ -386,7 +387,7 @@ paths:
         200:
           description: Log found
           schema:
-            $ref:  '#/definitions/LogWrapper'
+            type: string
         404:
           description: Log not found.
           schema:
@@ -636,25 +637,6 @@ definitions:
         $ref: '#/definitions/Call'
         description: "Call object."
 
-
-  LogWrapper:
-    type: object
-    required:
-      - log
-    properties:
-      log:
-        $ref: '#/definitions/Log'
-        description: "Call log entry."
-
-  Log:
-    type: object
-    properties:
-      call_id:
-        type: string
-        description: Call UUID ID
-      log:
-        type: string # maybe bytes, long logs wouldn't fit into string type
-
   Call:
     type: object
     properties: