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
Merge branch 'chapter04'
[nl] Language and wording corrections. Introducing characters from ASCII
extended.
[nl] added diacritical characters. Added (start of) gitolite translation.
[nl] re-cloned local repository, copied other chapter4 over.
Merge branch 'chapter04v2' of github.com:Cpt-xx/progit into chapter04v2
[nl] Completed translating to Dutch, repaired a false "link" to "Simple
Setups" section (that section does not exist) and made it point to the
section where the ssh_keygen command is used.;sK
Merge remote-tracking branch 'author/master'
[nl] Language and wording corrections. Introducing characters from ASCII
extended.
[nl] added diacritical characters. Added (start of) gitolite translation.
[nl] Completed translating to Dutch, repaired a false "link" to "Simple
Setups" section (that section does not exist) and made it point to the
section where the ssh_keygen command is used.;sK
Merge branch 'chapter04v2' of https://github.com/Cpt-xx/progit into chapter04v2

Conflicts:
	nl/04-git-server/01-chapter4.markdown
Merge pull request #637 from Cpt-xx/chapter04v2

Chapter04v2
[nl] Revised earlier Dutch translation

Modified certain sentences and wordchoises to be (hopefully) more
consistent with actual use of jargon in Dutch.
[nl] Revised earlier Dutch translation

Modified certain sentences and wordchoises to be (hopefully) more
consistent with actual use of jargon in Dutch.
Merge branch 'chapter01' of github.com:Cpt-xx/progit into chapter01
Merge branch 'de/next'
[de] Update localization summary in README