Readme grammer fix

"Giving THE developer...." -> "to express all THEIR application's.."
A developer is single.
"Their" refers to plural (multiple developers).
So, adjusted to plural ("developers") so that the two will match.
 * The alternative would be to use "his / her" but that leads to gender reference issues, so the former alternative works better

Signed-off-by: Jonathan Saring <yoni@cocycles.com>

README.md

@@ -112,7 +112,7 @@ This is usually difficult for several reasons:
     of them handle it differently.
 
 
-Docker solves the problem of dependency hell by giving the developer a simple
+Docker solves the problem of dependency hell by giving developers a simple
 way to express *all* their application's dependencies in one place, while
 streamlining the process of assembling them. If this makes you think of
 [XKCD 927](https://xkcd.com/927/), don't worry. Docker doesn't