Organize main.rs differently in Rust projects

[brson]

Per discussion in #10, the way I chose to to put the binary source at src/bin/main.rs is awkward because it produces a binary called main, which has to be explained. Putting that file somewhere else would do the right thing by default and avoid the subject.

Today I think it would be better to move this somewhere else, probably either src/bin/kvs.rs or src/main.rs. Need to decide which is the better practice. I'm inclined to go with the former, as putting lib.rs and main.rs in the same folder is a bit confusing, with the source for both intermingling.

[sticnarf]

I agree it's better to just rename src/bin/main.rs to src/bin/kvs.rs. In case we need to add other executables, it looks better to place all executables in the same directory.

[brson]

FIxed.