Explicit the reason of some deps

Signed-off-by: Patrick Luca Fazzi <patrick91@live.it>

Author: pfazzi

tests/test_architecture.rs

@@ -66,9 +66,9 @@ fn test_architectural_rules() {
 
         .rules_for_crate("rust_arkitect::rust_file")
             .it_may_depend_on(&[
-                "std::path",
-                "syn",
-                "toml", // Why?
+                "std::path", // Used to navigate the file system and get the logical name of the module
+                "syn",       // Used to parse Rust code and build the AST
+                "toml",      // Used to read Cargo.toml and find the crate of the file
             ])
 
         .build();