Updated the composer.json to use the PSR-0 autoloading
Updated the composer.json to use the PSR-0 autoloading

The library is now compatible with PSR-0 so using this strategy is
recommended.
Thus, there is no dependency to ext-curl

webbab/CssToInlineStyles,barryvdh/CssToInlineStyles,tijsverkoyen/CssToInlineStyles,tijsverkoyen/CssToInlineStyles,webbab/CssToInlineStyles,stof/CssToInlineStyles,webbab/CssToInlineStyles,stof/CssToInlineStyles