Quote caps

According to https://github.com/CSNW/sql-bricks/issues/25, postgres automatically lower-cases column & table names included in SQL statements unless they are quoted, causing them to no longer match capitalized tables/cols in the DB.

This pull request adds automatic quoting of columns with any capital letters in them.

It doesn't handle auto-quoting of table names. I'll need to do that in a separate pull request -- it'll be a bit more work, as I need to pull the table-name handling into a central place (I've wanted to do this refactoring for other reasons as well).

I also added this to the docs & added the `AS` keyword to the docs.