Add Russian locale for version 2.3

Add missing translation to en.yml
update gems and fix failing test

I don't know why the i18n setup code was in there, but it seems to do nothing important
Merge pull request #1710 from AlexStein/russian_t10n

Add Russian locale for version 2.3
update tolk and update nl locale

tolk generated all the other locales too, but no changes to the content were made
update changelog
Remove duplicate changelog note

[ci skip]
put the javascript to handle marking todos complete in its own object with unique name

this should prevent concurrent running ajax calls to mess up the ui
move js genreated for ajax calls into their own object to prevent name clashes

I only modified the js that is most likely to be used in cocurrent calls. This because we
start the development of Tracks 3 that will change all js.
fix regression and refactor todos/update.js a bit
small refactorings of generated javascripts
update gems and nl locale
add some sleep timers to hopefully fix the travis failures
Revert "add some sleep timers to hopefully fix the travis failures"

this did not work

This reverts commit 420c80911ba46aaf7d33bf00e0b6adcd48ab33ed.
make Tracks run on subdir again
Remove trailing whitespace and tabs
Update Rails to 4.1.5
Fix hard reference to image asset

Fixes #1713
Merge pull request #1714 from TracksApp/clean-up-bad-whitespace

Cleanup tabs and trailing whitespace
Prune upgrading instructions to latest version only
Convert documentation to Markdown using Pandoc