update code to Swift 4.1

Sources/Parser.swift

@@ -108,7 +108,7 @@ public class TokenParser {
     let filtersWithDistance = allFilters
                 .map({ (filterName: $0, distance: $0.levenshteinDistance(name)) })
                 // do not suggest filters which names are shorter than the distance
-                .filter({ $0.filterName.characters.count > $0.distance })
+                .filter({ $0.filterName.count > $0.distance })
     guard let minDistance = filtersWithDistance.min(by: { $0.distance < $1.distance })?.distance else {
       return []
     }
@@ -167,10 +167,10 @@ extension String {
     // initialize v0 (the previous row of distances)
     // this row is A[0][i]: edit distance for an empty s
     // the distance is just the number of characters to delete from t
-    last = [Int](0...target.characters.count)
-    current = [Int](repeating: 0, count: target.characters.count + 1)
+    last = [Int](0...target.count)
+    current = [Int](repeating: 0, count: target.count + 1)
 
-    for i in 0..<self.characters.count {
+    for i in 0..<self.count {
       // calculate v1 (current row distances) from the previous row v0
 
       // first element of v1 is A[i+1][0]
@@ -178,7 +178,7 @@ extension String {
       current[0] = i + 1
 
       // use formula to fill in the rest of the row
-      for j in 0..<target.characters.count {
+      for j in 0..<target.count {
         current[j+1] = Swift.min(
           last[j+1] + 1,
           current[j] + 1,
@@ -190,7 +190,7 @@ extension String {
       last = current
     }
 
-    return current[target.characters.count]
+    return current[target.count]
   }
 
 }