Add Helpme

Helpme is a package that provides a `@helpme` macro. This macro takes a `begin` block as its only argument, runs the code, and, if an error is raised, it looks through its "database" for a similar error/example. If one is found, it gives the user a human-readable suggestion printed to INFO, then `rethrow`s the error.

I am developing this package because oftentimes Julia's default error messaging can be misleading, while the solution is as simple as using `{...}` instead of `[...]` or wrapping a macro return in `esc(...)`.