Fix README design

[hypermkt]

I made README design better and readable by using Markdown as same as others.

Before	After

[hypermkt]

@gauthierm Could you review this PR?

[sudofox]

@gauthierm hello hello, could we get some love here? it's a decent readme update

(side note, I can't seem to get this lib to work properly with composer, it doesn't seem to have the include paths set up properly for HTTP_Request2, and shows this include path when erroring out)

/var/www/lib/thirdparty/vendor/pear/console_getopt
/var/www/lib/thirdparty/vendor/pear/http_oauth
/var/www/lib/thirdparty/vendor/pear/net_url2
/var/www/lib/thirdparty/vendor/pear/pear-core-minimal/src
/var/www/lib/thirdparty/vendor/pear/pear_exception
/usr/share/pear
/usr/share/php

might be cuz http_request2 is missing

    "include-path": [
        "./"
    ],

[hypermkt]

Thanks!!