#13 Improve implementation of constructors

[Markus Elfring]

I have noticed that a couple of assignments are used in the constructor bodies.

Examples:
https://github.com/mregmi/ext2read/blob/master/ext2copyfile.cpp#L25
https://github.com/mregmi/ext2read/blob/master/ext2fs.cpp#L28

The recommended way for performing efficient construction is to use the initialisation list.
http://dietmar-kuehl.de/mirror/c++-faq/ctors.html#faq-10.6
http://cprogramming.com/tutorial/initialization-lists-c++.html
http://www.eng.cam.ac.uk/help/tpl/languages/C++/Thinking_in_C++/tic0143.html
http://www.informit.com/guides/content.aspx?g=cplusplus&seqNum=15&rl=1
http://goingware.com/tips/parameters/membervars.html