update documentation

add manual page. closes issue jceb#10

bump to version 0.5. closes issue jceb#2

bump version

first implementation for creating DesktopEntrys

- remove unused member DesktopEntry.entries
- make filename optional for creating a DesktopEntry object
- implement DesktopEntry.fromfile class method for creating a DesktopEntry
  object from a certain file or link
- implement DesktopEntry.write for writing the object to a file
- add -c/--create switch for creating DesktopEntrys
- sort list output from get_autostart_files
- implement comparison of DesktopEntry objects by filename

bump version to 0.2