Barely Not Embarrassing Anymore

• Added more user-facing functions (trakt.user.following / .followers / .friends) because maybe I want to throw networkD3 at my people
• Improve consistency with date variables: The .posix variables should be removed and the existing date variables should just be properly converted to POSIXct
• Improve documentation: Added @family tags to all functions to group them together
• Add a package vignette
• Minor fixes and non-breaking additions