[ru] chapter 2: Incorporate changes from commits 716e192 and aa83065

"Add --word-diff option description"
[ru] chapter 4: Incorporate changes from commit 192518071.

"Updated explanation of ssh protocols."
[ru] chapter 2: Translate figures.
spelling fixes, translation improvements
Merge pull request #440 from gibas/spelling-fixes

spelling fixes, translation improvements
Merge pull request #439 from GArik/RU

[ru] Sync translation with the original and translate one more figure
[ru] Update chapter 4

Fix some punctuation problems.