Remove all base64 methods

Source/Shared/Extensions/String+Cache.swift

@@ -29,19 +29,3 @@ extension String: Cachable {
     return data(using: String.Encoding.utf8)
   }
 }
-
-// MARK: - Helpers
-
-/**
- Helper String extension.
- */
-extension String {
-  /**
-   Creates base64 string
-   - Returns: A base64 encoded string
-   */
-  func base64() -> String {
-    guard let data = self.data(using: String.Encoding.utf8) else { return self }
-    return data.base64EncodedString(options: NSData.Base64EncodingOptions(rawValue: 0))
-  }
-}

Source/Shared/Storage/DiskStorage.swift

@@ -304,7 +304,7 @@ public final class DiskStorage: StorageAware {
   /**
    Builds file name from the key.
    - Parameter key: Unique key to identify the object in the cache
-   - Returns: A md5 or base64 string
+   - Returns: A md5 string
    */
   func fileName(_ key: String) -> String {
     return MD5(key)

Tests/iOS/Specs/Extensions/String+CacheSpec.swift

@@ -7,20 +7,6 @@ class StringCacheSpec: QuickSpec {
   override func spec() {
     describe("String+Cache") {
 
-      describe("#base64") {
-        it("returns the correct base64 string") {
-          let items = [
-            "John Snow": "Sm9obiBTbm93",
-            "You know nothing": "WW91IGtub3cgbm90aGluZw==",
-            "Night's Watch": "TmlnaHQncyBXYXRjaA=="
-          ]
-
-          for (key, value) in items {
-            expect(key.base64()).to(equal(value))
-          }
-        }
-      }
-
       describe("Cachable") {
 
         describe(".decode") {