*: switch to github.com/ghodss/yaml for more consistent YAML parsing

ghodss/yaml converts from YAML to JSON before attempting to unmarshal.
This allows us to:

* Get the correct behavor when decoding base64'd []byte slices.
* Use *json.RawMessage.
* Not have to support extravagant YAML features.
* Let our structs use `json:` tags

connector/github/github.go

@@ -19,10 +19,10 @@ const baseURL = "https://api.github.com"
 
 // Config holds configuration options for github logins.
 type Config struct {
-	ClientID     string `yaml:"clientID"`
-	ClientSecret string `yaml:"clientSecret"`
-	RedirectURI  string `yaml:"redirectURI"`
-	Org          string `yaml:"org"`
+	ClientID     string `json:"clientID"`
+	ClientSecret string `json:"clientSecret"`
+	RedirectURI  string `json:"redirectURI"`
+	Org          string `json:"org"`
 }
 
 // Open returns a strategy for logging in through GitHub.