[FIRST] plotlyupdate.m

@chriddyp wanna look this over when you get a chance. 

plotlyupdate
plotlyupdate('verbose') 
ploltyupdate('verbose','nocheck') 
we might want to drop `plotlyDirs` here. I can imagine that some people who hack work on projects that incorporate  plotly might actually place their project code inside the plotly directory, e.g.  `/Users/chris/my_research_project/plotly`