[#7] Allow factoids to be word case agnositc.

Allows for factoids to not care about case, as per #7.

Example:

```
[21:36:22] <@eojthebrave>	lubot: joe is awesome
[21:36:22] <lubot>	eojthebrave: Okay!
[21:36:25] <@eojthebrave>	Joe?
[21:36:25] <lubot>	Joe is awesome
[21:36:28] <@eojthebrave>	Joe!
[21:36:28] <lubot>	Joe is awesome
[21:36:32] <@eojthebrave>	joe!
[21:36:32] <lubot>	joe is awesome
[21:36:49] <@eojthebrave>	JOE?
[21:36:50] <lubot>	JOE is awesome
[21:36:52] <@eojthebrave>	joE
[21:36:59] <@eojthebrave>	delete factoid JoE
[21:36:59] <lubot>	eojthebrave: Okay!
[21:37:02] <@eojthebrave>	joe?
```

Resolves #7