Get 30 tweets when started, insted of 10.
Mention to all members of replied tweet by default.
Many important changes (yes, this is bad commit...)

* Now we have tweet button, and [enter] means simply inserting linefeed.
* Show a linefeed in a tweet as linefeed.
* Redesign main form for adding tweet button.
* Now we can get old tweet from a link at the bottom of timeline.