not to scroll a column content when retrieving a gap

Most user reads tweets in a reverse chronological order (from new to
old direction). After retrieving tweets in a gap it is convenient for
the user to see the newest tweet that he will read next. Crowy should
prevent the column content from scrolling.
To update tweet timestamps periodically

Tweet timestamps displayed in the short form relative to the current
time are updated periodically. The interval between updates is 57
seconds. The value of timestamp of each tweet is stored using jQuery’s
data method with the “time” key, i.e. $(tweetElement).data(“time”,
timestamp). The title attribute showing the date and time in the
original Crowy format is added to each timestamp link.
更新ボタンを押したら先頭にスクロール

更新ボタンを押したら先頭にスクロールして、読み込んだ最新のツイートが表示されるようにする。
Merge pull request #13 from mg6tqq/gap-noscroll

not to scroll a column content when retrieving a gap