Initialize tests

[peter279k]

Changed log

• Initialize tests.
• Require the phpunit/phpunit package and it defines onrequire-dev block in composer.json.
• It should require the mbstring extension because this repo uses the related functions.
• The openssl and sodium extensions are optional extension and they should be mentioned on suggest block in composer.json.

[lablnet]

@peter279k Thanks you so much for contribution

i fix copyright comment as you see my commit and the first argument is key
$encryption = new Encryption('12345678990-=====-===','openssl');

[peter279k]

@lablnet, thank you for your reply.

I forgot that the Encryption::__construct arguments order has been changed.

I think we should add the Travis CI integration on this repository so that it can help someone to do contribution easily :).

[lablnet]

ac1449b

[lablnet]

@peter279k this test is fail, do you know why?
because i didn't work with tests before.

[peter279k]

@lablnet, thank you for your reply.

Actually you should add the libsodium package manually.

I will create the PR for you about the correct Travis CI build setting.

[lablnet]

okay thanks you so much
@peter279k