Add missing import

The early module map refactor left SQLCipher users high and dry :(

This should fix stephencelis#100.

Signed-off-by: Stephen Celis <stephen@stephencelis.com>

Author: stephencelis

SQLiteCipher/Cipher.swift

@@ -22,6 +22,8 @@
 // THE SOFTWARE.
 //
 
+import sqlite3
+
 extension Database {
 
     public func key(key: String) {