Merge pull request qmlbook#92 from qmlbook/ch06-summary

summary.md: fix language issues

docs/ch06-controls/summary.md

@@ -1,7 +1,7 @@
 # Summary
 
-In this chapter we have looked at the Qt Quick Controls 2. They offer set of elements that provide more high level concepts than the basic QML elements. For most scenarios, you will save memory and gain performance by using the Qt Quick Controls 2, as they are based around an optimized C++ logic instead of Javascript and QML.
+In this chapter we have looked at Qt Quick Controls 2. They offer a set of elements that provide more high-level concepts than the basic QML elements. For most scenarios, you will save memory and gain performance by using the Qt Quick Controls 2, as they are based around optimized C++ logic instead of Javascript and QML.
 
-In the chapter we’ve demonstrated how different styles can be used, and how a common code base can be developed using file selectors. This way, a single code base can address multiple platforms with user interactions and visual styles.
+We’ve demonstrated how different styles can be used, and how a common code base can be developed using file selectors. This way, a single code base can address multiple platforms with different user interactions and visual styles.
 
-Finally, we have looked at the Imagine style that allows you to completely customize the look of a QML application through the use of graphical assets. This way an application can be reskinned without any code change what so ever.
+Finally, we have looked at the Imagine style, which allows you to completely customize the look of a QML application through the use of graphical assets. In this way, an application can be reskinned without any code change whatsoever.