[Change] `listdate` now finds all dates of the format yyyy-m-d

 * This means that curly brackets are not longer needed.
 * This also has the side effect that a line will be listed under multiple
     dates if present in that line. e.g. added date, due date, tickler
     date, completed date, etc.
 * This probably breaks the expected fucntion of the '-#' switch (hide dates)
Proper linewraps for all list options

Really closes #1
Fixes an issue where if prepend date feature was active and the added line had a priority in it, it would have an extra space after the added date.

$ todo.py add '(A) test'
output was: '(A) 2013-12-10  test'
output now: '(A) 2013-12-10 test'
[Feature] `top` command

the `top` command lists the top 16 items on the todo list, when sorted
by priority (like listpri)