case insensitive username

[lefnire]

many people are logging in with improper case, evidently it's actually standard to not check uname case sensitivity.

One nice thing about case-sensitive usernames is that, as habitrpg grows, it'll give new users more flexibility in creating their accounts. The obvious drawback is the increased potential for failed logon attempts, which result in frustrated end users. I'm not sure if the benefits outweigh the risks.