Wrong type with malice-plugins/yara

[stanley101music]

I've added https://github.com/malice-plugins/yara/tree/master to the configuration file.
The error appears in /main/rule_processors.py in function evaluate_yara_rule_score at line 517
where the meta_data is str not dict, and thus doesn't have items()

Here's the original yara rule that caused this error from https://github.com/malice-plugins/yara/blob/master/rules/rats.yar

rule Albertino
{
	meta:
		author = " Kevin Breen <[email protected]>"
		date = "2014/04"
		ref = "http://malwareconfig.com/stats/AAR"
		family = "albertino"
		tags = "rat, albertino"

	strings:
		$a = "Hashtable"
		$b = "get_IsDisposed"
		$c = "TripleDES"
		$d = "testmemory.FRMMain.resources"
		$e = "$this.Icon" wide
		$f = "{11111-22222-20001-00001}" wide
		$g = "@@@@@@@@@@@"

	condition:
		all of them
}

and the metadata of the rule that is sent as the input of evaluate_yara_rule_score is
'metadata': {'tags': 'ALBERTINO, RAT'}

Compared to other normal metadata, it seems that the type of the value of metadata should be a list of dictionaries,
while in this case, the type of the value is dictionary.

[Neo23x0]

This should fix the issues : #18