Merge pull request #550 from Maxqia/convert

[enh] currency_convert: allow strings like google's "convert 1 euro to dollars"

searx/engines/currency_convert.py

 url = 'https://download.finance.yahoo.com/d/quotes.csv?e=.csv&f=sl1d1t1&s={query}=X'
 weight = 100
 
-parser_re = re.compile(u'^\W*(\d+(?:\.\d+)?)\W*([^.0-9].+)\W+in?\W+([^\.]+)\W*$', re.I)  # noqa
+parser_re = re.compile(u'.*?(\d+(?:\.\d+)?) ([^.0-9].+) (in|to) ([^\.]+)\W*$', re.I)  # noqa
 
 db = 1
 
         # wrong query
         return params
 
-    ammount, from_currency, to_currency = m.groups()
+    ammount, from_currency, none, to_currency = m.groups()
     ammount = float(ammount)
     from_currency = name_to_iso4217(from_currency.strip())
     to_currency = name_to_iso4217(to_currency.strip())