STL vector.size() returns size_t so compare against that.
Add the ability to set the file type as a command line option.

Change the return type of validateOutputFile to help with logic.
Change a few variable types to be more accurate.
Should not remove this value.

All file types currently supported have 3 characters and we can only
get into the loop if that is the case. Therefore remove 4 characters,
including the 'dot'.
Merge branch 'FileType'

The filetype can now be set when the code is run so there is no need
for the user to alter and recompile the source code. Probably didn't
need a new branch for this, but I believe it is the suggest technique
when working with a git repo so why not.

Lets use size_t when appropriate, I'm not going to go looking for places
where it needs to be corrected, but if I set it...