Delete pid file afterwards on Windows
Fix default dispatch of Vim command
Separate :Start from dispatch#start
Stopgap solution for projectile.vim

I want to be able to change the working directory for the default
:Start, but it's not clear how that should work, so I'm cheating and
adding a special case for projectile.vim.  Sue me.
Allow greater errorformat control with g:dispatch_compilers

References #10, #42, #43.