Truncate names to 40 characters

[toddtreece]

Why

We were seeing some events being recorded for android but not for iOS, and it seems like the cause is a string length limit in Firebase. It looks like others are seeing this issue as well: #20

The Firebase docs specify a length limit of 40 characters for event names, event parameter names, and screen names:

Should contain 1 to 40 alphanumeric characters or underscores.

It seems like this is already implemented in analytics-android-integration-firebase.

What

• adds shared method to format event names, param names, and screen names
• adds test coverage

[bsneed]

Thanks @toddtreece !