PSR-4 autoloading support.

[sikhlana]

To improve the usage of this wonderful library, I've added autoloading support of the classes compliant with the PSR-4 standard. This is needed because currently it's a hassle to include the classes by adding:

require_once base_path().'/vendor/yourivw/leclient/LEClient.php';

in each and every file that uses the client library. Whereas, composer can handle it just by installing the package, call the class and voila!

Major changes in this PR includes:

• Set the minimum PHP version to 7.1 as per the README.
• Added the \LEClient namespace.
• Moved all the examples to examples/ directory.
• Bug fix related to a missing variable. Reference: https://github.com/yourivw/LEClient/commit/0438ad408491b0acca5427d8f93076b3dcdd7958.

[yourivw]

Added to master branch and version 1.1.4. Removed PHP minimum version 7.1. Was already changed in previous PR but never updated in readme.

[sikhlana]

Okay, cool. Though I do believe you should remove support for 5.2 as it's EOL and support for security updates for 5.6 is ending soon too.