adding GetStringMapStringSlice method

viper.go

diff --git a/viper.go b/viper.go
index a65a33a..f68226b 100644
--- a/viper.go
+++ b/viper.go
@@ -465,6 +465,12 @@
 	return cast.ToStringMapString(v.Get(key))
 }
 
+// Returns the value associated with the key as a map to a slice of strings
+func GetStringMapStringSlice(key string) map[string]string { return v.GetStringMapStringSlice(key) }
+func (v *Viper) GetStringMapStringSlice(key string) map[string]string {
+	return cast.ToStringMapStringSlice(v.Get(key))
+}
+
 // Returns the size of the value associated with the given key
 // in bytes.
 func GetSizeInBytes(key string) uint { return v.GetSizeInBytes(key) }