Better UX: retina ready, same width, better visualization of '.'

[liuggio]

• as commented here: Add badge in README to show totat download and latest stable release symfony/symfony#8308 (comment) could be great to be retina ready. Is not possible to do it because the markdown specification does not allow to specify image dimension.
• the badges now have different widths (1 pixel of diff)
• if you see this the dot readability could be improved

[agiuliano]

👍

[wouterj]

The overal readability of the badge and the contrast are to low to make me read it.