define functions to render and display an UML file

there's also a keyboard shortcut available (C-c C-c) to render and
display the UML diagram.
use plantuml-run-command, style fixes
fixed typo
Merge pull request #3 from tosmi/master

provide keyboard shortcut to render and display the UML diagram
Modified so that in-file works with spaces

Modified plantuml-mode so that spaces in the file name path for temporary plantuml in-file works with spaces.
Merge pull request #4 from dentrinh/master

Modified so that in-file works with spaces