Support provided for failing of an Invisible character and Randomised insertion of zwc stream

Updates

• Fixed the bug by removing an invisible character ( U+2060 ) due to visibility in CJK (Chinese Japan Korea) font family.
  For further information, it is related to issue #12.
• Randomised the position of insertion of zwc stream in the cover message and updated stegcloak to support backward compatibility.
  Detailed discussion is available in #15.

Stegcloak v1.1.1 is stable and published.