docs(README.md): fix path to source folder
fix(documents): fix several typos

Using:
for file in `find -name '*.html.eco'`; do aspell --lang=en_US --mode=html --add-html-skip=code --dont-backup check $file ; done
style(documents): remove trailing white space

Usgin:
find -name '*.html.eco' | xargs sed -i 's/\s\+$//'
Merge branch 'master' of https://github.com/falko/camunda.org into falko-master

Conflicts:
	site/src/documents/get-started/developing-process-applications.html.eco