Added license for SecretTextView

Added license for matthewrkula/SecretTextView library which was mentioned as "Unknown License" earlier.

README.md

@@ -190,7 +190,7 @@ Name | License | Demo
 [Titanic](https://github.com/RomainPiel/Titanic) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | <img src="/art/Titanic.gif" width="100%">
 [MatchView](https://github.com/Rogero0o/MatchView) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | <img src="/art/MatchView.gif" width="49%">
 [android-autofittextview](https://github.com/grantland/android-autofittextview) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | ![](/art/android-autofittextview.gif)
-[SecretTextView](https://github.com/matthewrkula/SecretTextView) | UnKnown | ![](/art/SecretTextView.gif)
+[SecretTextView](https://github.com/matthewrkula/SecretTextView) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | ![](/art/SecretTextView.gif)
 [TextJustify-Android](https://github.com/bluejamesbond/TextJustify-Android) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | <img src="/art/TextJustify-Android.png" width="100%"> <img src="/art/TextJustify-Android2.jpeg" width="100%">
 [RoundedLetterView](https://github.com/pavlospt/RoundedLetterView) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | <img src="/art/RoundedLetterView.png" width="49%">
 [TextDrawable](https://github.com/amulyakhare/TextDrawable) | [Apache License V2](https://www.apache.org/licenses/LICENSE-2.0) | <img src="/art/TextDrawable.png" width="49%"> <img src="/art/TextDrawable2.png" width="49%">