Implemented tests for imageboard

[SamuelMarks]

Note: this isn't [yet] ready for being merged. PR created to facilitate discussion.

Questions:

1. I've included typings, because that's what you've been doing. However, I've also added a tsd.json, so now people can get the package manager to populate that directory (like they would node_modules). Should I add typings to .gitignore?
2. npm test now does a mocha --compilers ts:typescript-require -u exports -R spec tests/test_*.ts. Is that the approach you prefer?

Improving test coverage once these initial tests are in the folder should be trivial.

[DanielRosenwasser]

Hey @SamuelMarks thanks for taking this on. I think the correct thing to do was just to use tsd.json. We're eventually going to remove the typings files, so if you could remove them altogether that would be ideal.

For the second question, I don't think we had a specific preference. If you have a better idea in mind, I think we'd welcome it. What were you thinking?

[SamuelMarks]

@DanielRosenwasser: No worries. Okay, it's now ready to merge.

Would you like me to squash all my commits into one?

[DanielRosenwasser]

@SamuelMarks no I think this is fine, though, I think other projects relied on the same node.d.ts. @mhegazy any idea about this?