enable parallel check of languages

Use parallel to spawn as many subprocesses as possible to accelerate
the tests.
Change Maruku check to fully functional mode

this is cleans up the code.
Force output of Rake messages to stderr
Fix typos
Fix typos
Fix typos
[nl] Replace all occurences of the verb ‘clone’ by its dutch translation ‘klonen’
format latex longtables

Now pandoc uses the package longtable of latex to manage tables. The
default setup does not restrict column width. The explanation column
must be constrained to fit in the page's width.
Monospace branch names
Monospace branch names
Complete the long unfinished paragraph...
Update 01-chapter1.markdown

check for mistakes
add "sudo" by ubuntu package installation
...
Add new directory for Vietnamese translation
Mention translated files in README

The files which are not yet started in translation should not be part of
the files in the language. Otherwise, we need to always backport the
changes to the original english to all "not yet"/"will never be"
translated files in partially translated languages.
Add table numbering to longtables
Add second chapter, to start on the most essential
Esperanto: translate a little more
Esperanto: Correct image description
Esperanto: start of chapter 2, probably the most essential chapter...
Esperanto: complete the first part of chapter 2