Fix errors when using root (/) as TARGET_DIR (#25)

Previously, using `/` as `TARGET_DIR` lead to a situation where the
string got converted to an empty string when trimming away the trailing
slashes.

This PR fixes the issue by updating the `trim_trailing_slash` method to
skip trimming for strings with length `1`.

Co-authored-by: {{NAME}} <{{EMAIL}}>

src/lib.rs

@@ -192,7 +192,11 @@ impl<'a> Arguments<'a> {
 
     fn trim_trailing_slash(string: &str) -> &str {
         if let Some(b'/') = string.as_bytes().last() {
-            &string[..string.len() - 1]
+            if string.len() == 1 {
+                string
+            } else {
+                &string[..string.len() - 1]
+            }
         } else {
             string
         }