Editing @done doesn't remove strikethrough

[jessegrosjean]

For my proposed solution please see:

Proposal, require that both ( and ) are always escaped in tag values?

The current tag syntax is creating at least one bug in my code and some some confusion when others are trying to read TaskPaper files. I think the solution is to force that ( is escaped in addition to ) which already must be escaped. Unfortunately this change will bread existing tag values that have unescaped (s. The root of the problem is when you write @tagname( everything that follows is considered tag value up until an unescaped ) is encountered. In some cases this causes confusion, but…