Preemptively verify that name+kaomoji will fit within size constraints.

20 characters is currently the limit for display names for Twitter.

If there are no kaomoji that fit, or the user's name is too long to begin with, it will raise an error.
Add option to consider only new tweets instead of the last 100.

If there are no new tweets, consider the current emotion to be neutral.
Merge pull request #7 from elena-v2/testing

Preemptively verify that name+kaomoji will fit within size constraints.
Merge pull request #8 from elena-v2/sample-recent

Add option to consider only new tweets instead of the last 100.