Update php-curl-class version up to 9

[xoxefdp]

Fixings:

• Update php-curl-class version required >= 9

Requirements by fix

• Added php version required >= 7 (required by php-curl-class >= 9)
• Added curl extension as required (required by php-curl-class)

Features

• Added mbstring extension as suggested (referenced by php-curl-class)
• Added gitignore file

Solves #26