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
[ja] Apply c267f27
[pt-br] Update 01-chapter4.markdown

[pt-br]

Concordance, punctuation, plural and another mistakes corrected.

Concordância, pontuação, plural e outros erros corrigidos.
Merge pull request #550 from nmoura/patch-6

[pt-br] Update 01-chapter4.markdown
Update 01-chapter3.markdown

General translation fixes
Update 01-chapter3.markdown

General fixes
Merge pull request #551 from paulodrjr/master

[pt-BR] Update 01-chapter3.markdown
Merge pull request #543 from harupong/ja-chapter3

[ja] Apply c267f27
Remove unnecessary comments
Switch font for pdf to IPAexMincho
Merge pull request #554 from harupong/latex-fonts

[ja]Switch font for pdf to IPAexMincho
svn log searches revisions in the whole repository
Merge pull request #552 from radeksimko/svn-migration-correction

Migration of users from SVN to Git may fail
[de] Translate chapter 6.4 (complete new translation)
Merge pull request #556 from progit-de/master

[de] Translate chapter 6.4 (complete new translation)
[de] Translate chapter 6.5 (complete new translation)
[de] Update german project progress in Readme file
Merge pull request #560 from progit-de/master

[de] Translate chapter 6.5 (complete new translation)