Add badge poser in README

[agiuliano]

Add statistic about total download and latest stable release
See https://github.com/PUGX/badge-poser

[lsmith77]

interesting .. final output can be seen here https://github.com/agiuliano/LiipImagineBundle/

[havvg]

I'm +1 on the stable badge. But I see no use in the download one, especially because most likely the least CIs have disabled the packagist notifications :) Never trust statistics.

[agiuliano]

Badge poser shows the exact information you can see on packagist site, btw is possible to show the most interesting badges

[liuggio]

@havvg eheh never trust stats :), btw for me the download badge is not so useful as stable version, but is good if you want to show how much the library has been used by real developer (not CI).

[havvg]

@liuggio That's the point, you cannot tell how many real developer are using the library by utilizing the download statistics of packagist. It's just simply counting, it doesn't know whether I actually installed the package - as in a new project using it - or I deployed it again e.g. on a composer aware PaaS, which "installs" it. But this install/download counter does not reflect "popularity" or similar aspects you would expect by such a number.

[liuggio]

I'm totally with you, but is not so important 'the' number, because this badge answers to a simple question: is this library popular? and that 'k' means yes a lot.

[havvg]

Ok.