<p>By any measure, the story of the Scottish National Party is an extraordinary one.<br>Forced to endure decades of electoral irrelevance since its creation in the 1930s, during which it often found itself grappling with internal debate on strategy, and rebellion from within its own ranks, the SNP virtually swept the board in the 2015 general election, winning all but three of Scotland's fifty-nine seats in Westminster. What's more, und...