DOC: HelloWorld Comments Edit for ITKSoftwareGuide

Corrected the use of an apostrophe and replaced 'Insight' with
ITK. It seems it should be either the whole thing 'Insight
Registration and Segmentation Toolkit' or ITK for consistency.

Change-Id: Ibac23d4b72290387d701d6707cb4015ba9901062
Merge topic 'HelloWorldCommentsEdit'

86552faa DOC: HelloWorld Comments Edit for ITKSoftwareGuide