Usernames are unnecessarily case-sensitive.

[skx]

I appreciate that the usernames ultimately come from twitter, but usernames over there aren't case-sensitive.

For example I have an account on Twitter with username Stolen_Souls and both these links work:

• https://twitter.com/Stolen_Souls
• https://twitter.com/Stolen_SOULS

By contrast only the first of these two links succeeds:

• https://www.openhunt.co/@Stolen_Souls
• https://www.openhunt.co/@Stolen_SOULS

[skx]

See #49 for one possible patch.