Small fixes for package README files.

Author: pavoljuhas

README.txt

@@ -28,7 +28,7 @@ the system package manager:
 
 For other Linux distributions use the respective package manager to install
 these packages.  Note there may be somewhat different names.  PDFgui should
-work on other Unix-like operating systems and on MAC as well.  Please, search
+work on other Unix-like operating systems and on Mac as well.  Please, search
 the web for instructions how to install external dependencies on your
 particular platform.
 

diffpy/pdfgui/applications/pdfgui.py

@@ -24,7 +24,7 @@
 
 Options:
   -h, --help      display this message
-  -V, --version   show script version
+  -V, --version   show program version
 
 Debugging options:
   --db-noed       disable exceptions catching to ErrorReportDialog