refactor package main (#49)
refactor package main (#49)

move the contents of main.go into app package.
scaffold a CLI subcommands package. 
add a version package and add /_version handler to print detailed version info. 

groob/micromdm,micromdm/micromdm,micromdm/micromdm,groob/micromdm,natewalck/micromdm,mosen/micromdm,mosen/micromdm