Merge pull request #1 from carloslima/master

Smallish changes
Added contributors section
Merge pull request #2 from carloslima/master

Recognizes Desktop Environment and set wallpaper accordingly
Perl::Tidy code
POD documentation
added vim backup to gitignore
Made it compatible with MacOSX
fixed uninit error of env without XDG_CURRENT_DESKTOP
Merge pull request #3 from ohoushyar/master

MacOS Compatibility
Updated contributors list
POD formatting
Perl::Tidy code
Add support for setting background image in OS X
Alternate image link
Merge remote-tracking branch 'naviltsev/osx-support'

Conflicts:
	natgeobg.pl
Documentation improvement
Bugfix