Update README.md

Author: skarlsson

README.md

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 # postgres-asio
 =========
 
-A C++11 asyncronous postgres client library based on boost::asio. The library provides a thin skin on to of the C-API pglib
+A C++11 asyncronous postgres client library based on boost::asio. The library provides a thin skin on top of the C-API pglib
 
 
 Platforms: Windows / Linux