[#5] Allow for the string !who in a factoid to be replaced with querying user's nick.
[#3] Allow use of both is and are to set factoids.
[#2] Allow for <reply> style factoids.
Code cleanup per review.

- Use util.format to format response string.
- Simplify ternary operator check for is_reply variable.
Merge pull request #27 from Lullabot/5-who

[#5] Allow for the string !who in a factoid to be replaced with querying user's nick