Several updates

[u8sand]

• Updated url: intro => url: /intro in TOC, this refused to compile without it on my system
• Removed a stray :Q in Makefile and a stray temporary file Makefile~, someone uses vim ;)
• Added temporary files *~ to gitignore
• Fixed a deprecation warning about bundle --path, I'm hoping this wasn't a breaking change for older versions of ruby

There are currently TONS of warnings on running make serve; we should likely address them sooner than later but in the interim you can suppress them with i.e RUBYOPT="-W0" make serve

[u8sand]

NOTE: I moved the latest commit of this patch to a new PR