explicitly require ruby >= 1.9.3, added newline after question with noecho

Since [1.9.2 is EOL](https://www.ruby-lang.org/en/news/2014/07/01/eol-for-1-8-7-and-1-9-2/) and we now use features only available for ruby 1.9.3 and newer, i've added this requirement to the gemspec and mentioned it as a breaking change in the changelog.

Also as was pointed out by @danevron in PR #1112 noecho also would not echo the newline and thus a subsequent question is printed into the same line. Therefore I've manually added a newline to stdout.