plantuml.jar upgraded from 7931 to 7958
Merge pull request #4 from vistrcm/plantuml_upgrade

plantuml.jar upgraded from 7931 to 7958
Diagrams rendered to same folder as source file, added Preview as viewer, User setting for viewer
whitespace cleanup
less verbose automatic filenames
restore autodetection as a fallback
use a dummy filename for rendering unsaved buffers
render whole file if no selections

As suggested by Julian Godesa.
documentation updates
plantuml update
cursory install instructions
Quick 2to3 pass
Added a missing error_message import
Added a missing error_message import
str/bytes fixes
Defer setup() call in ST 3
Added Menu.sublime-menu
Python 2/3 import support
*Of course* that would be a ValueError, not an ImportError
Added "Display Diagrams" menu