Escape spaces in path

The command :make is not working when you have spaces in your path. The code adds escapes spaces with a "\" sign.  

You have also add this line into your .vimrc:

    let g:plantuml_executable_script='java -jar /path/to/plantuml.jar -v'

The suggested script which has to be placed into a plantuml file doesn't worked for me.
Merge pull request #4 from Konafets/master

Escape spaces in path