breadshot: expand ~ in save_dir, align Cargo.toml version with tag

- config.rs: expand a leading ~ in the save_dir config value on load.
  The documented example config (save_dir = "~/Pictures/Screenshots")
  was previously taken literally, silently creating ./~/Pictures/... in
  the current working directory. Added unit tests.
- Cargo.toml: 1.0.0 -> 0.1.0, matching the only existing tag (v0.1.0).
  breadshot --version previously reported nine releases ahead of the
  actual release history.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "breadshot"
-version = "1.0.0"
+version = "0.1.0"
 edition = "2021"
 license = "MIT"
 authors = ["Breadway"]