change to have i18n with relative time from moment

@pliman

I made changes so that if the moment language changes, the strings stay up-to-date. ie. don't create the strings on initialization

As well, there were issues with the 'de' language (plus others) that use a function for some of the date strings as opposed to just a simple string, so I used the moment humanize function and changed the  default thresholds. it will need https://github.com/moment/moment/issues/1715 to be fixed for this to be merge-able.

This does not fix the "a few seconds" issue.

Please consider merging this pull request to fix the issue you had mentioned for i18n and provide further support for languages.