read(f, :varname) + readsafely(f, :varname)

I usually like to use `Symbol`s rather than `String`s when referring to things that are variable names, so I've been buggered for a while that `read` didn't take symbol arguments for the name of the thing to read. This should add that.

I haven't done any more elaborate testing of this than to just try it manually on a `jld` file I had laying around, and although I did glance at the test files I didn't really see the logical place to add tests for this. On the other hand, there is basically no logic here, so there's probably very little that can go wrong.