Tag Assignment Scoring Improvement

[jmbarne3]

Description
Add additional calculation to the tag score that weights the additional points awarded for the number of events assigned to the tag. Currently, the value being added to the score is equal to the number of events assigned to the tag. This is going to over-inflate the score of some tags to the point where the additional 200 points awarded for being a "promoted" tag won't bump those tags to the top.

Why it's Important
We need to normalize the score awarded for number of events the tag is assigned to in order to give the magic number awarded for promotion less arbitrary. Without normalizing this value, we will have to continually update the value of the promotion score to make it meaningful in the score calculation.

Possible Implementation
We can divide the number of events a tag is assigned to by the maximum number of events any tag is assigned to. This would have the effect of clamping the value between 0 - for tags that have less than 0.5% of the maximum number of tags assigned - and 100 - for the one tag that currently has the maximum number of events assigned.

Additional context
In order to make this practical, we're going to need a way of caching the value we're dividing by (the maximum number of events assigned to any one tag). The query to pull this number is going to be inefficient enough that we're not going to want to run it every time we pull tags.

In addition, we're probably going to want some sort of temporal limit to the tags we're looking at. For example, we may want to calculate the "assigned to" score based on the number of events the tag has been assigned to in the last 3-6 months. This will also add some complexity to the query, further making it necessary to cache this value.