Fix day 1 rtweet example

[bensoltoff]

Twitter API is janky. Already corrected in the slides. Just need to fix the notes.

[bensoltoff]

Also replace exercise on API week.

[bensoltoff]

Day 1 example has been fixed. Need to revise the exercise code to use the newest version of rtweet.

• Add instructions to install rtweet from GitHub directly for new authentication protocol
• Use following code to store/retrieve authentication token

# authenticate interactively with bearer token from my Twitter app
auth <- rtweet_app()

# store token
auth_save(auth, "some-name")

# retrieve stored token
auth_as("some-name")

• Securely share the bearer token with the class so it doesn't get me banned from Twitter API
• Adjust exercise to not require group_by(screen_name) since that is not automatically included in the API results