Add bundler documentation.
Add bundler documentation.

alexclarkofficial/docs,rchavarria/docs,spazm/docs,ZacharyRSmith/docs,yurrriq/docs,lfex/exercism-docs,NobbZ/docs,NobbZ/docs,spazm/docs,k4rtik/docs,yurrriq/docs,rchavarria/docs,alexclarkofficial/docs,exercism/DEPRECATED.help.exercism.io,ZacharyRSmith/docs,canweriotnow/docs,ekse/exercism-docs,lfex/exercism-docs,ekse/exercism-docs,arashbi/docs,k4rtik/docs,arashbi/docs,exercism/DEPRECATED.help.exercism.io,canweriotnow/docs