do not add newline to all strings (#31)

cc/ @AucaCoyan 

this PR moves the `add_newline_at_end_of_file` outside of
`format_inner`.
the responsibility is not those of `format_single_file`, `format_string`
does not add a newline to all strings anymore.

tests have been fixed 👍 

one thing i'm struggling with is the following test
```rust
    #[test]
    fn remove_additional_lines() {
        let input = "let one = 1\n\n\n";
        let expected = "let one = 1\n";
        run_test(input, expected);
    }
```
which does not pass without the `\n` in `expected` 🤔 
**any idea?** 😕

src/formatting.rs

@@ -104,7 +104,6 @@ pub(crate) fn format_inner(contents: &[u8], _config: &Config) -> Vec<u8> {
 
  start = span.end + 1;
  }
- out = add_newline_at_end_of_file(out);
 
  out
 }
@@ -116,7 +115,7 @@ fn insert_newline(mut bytes: Vec<u8>) -> Vec<u8> {
 }
 
 /// make sure there is a newline at the end of a buffer
-fn add_newline_at_end_of_file(out: Vec<u8>) -> Vec<u8> {
+pub(crate) fn add_newline_at_end_of_file(out: Vec<u8>) -> Vec<u8> {
  match out.last() {
  Some(&b'\n') => out,
  _ => insert_newline(out),

src/lib.rs

@@ -2,7 +2,7 @@
 //!
 //! It does not do anything more than that, which makes it so fast.
 use config::Config;
-use formatting::format_inner;
+use formatting::{add_newline_at_end_of_file, format_inner};
 use log::{debug, trace};
 use std::fs::File;
 use std::io::Write;
@@ -16,7 +16,7 @@ pub fn format_single_file(file: &PathBuf, config: &Config) {
  let contents = std::fs::read(file)
  .unwrap_or_else(|_| panic!("something went wrong reading the file {}", file.display()));
 
- let formatted_bytes = format_inner(&contents, config);
+ let formatted_bytes = add_newline_at_end_of_file(format_inner(&contents, config));
 
  if formatted_bytes == contents {
  debug!("File is formatted correctly.");
@@ -59,21 +59,21 @@ mod test {
  \"a\": null
  }
 ]";
- let expected = "[{\"a\":0},{},{\"a\":null}]\n";
+ let expected = "[{\"a\":0},{},{\"a\":null}]";
  run_test(input, expected);
  }
 
  #[test]
  fn echoes_primitive() {
  let input = "1.35";
- let expected = "1.35\n";
+ let expected = input;
  run_test(input, expected);
  }
 
  #[test]
  fn handle_escaped_strings() {
- let input = " \"hallo\\\"\"";
- let expected = "\"hallo\\\"\"\n";
+ let input = "\"hallo\\\"\"";
+ let expected = input;
  run_test(input, expected);
  }
 
@@ -103,21 +103,14 @@ def my-func [
 ]{ print(param1) 
 }
 myfunc(one) 
-# final comment\n";
+# final comment";
  run_test(input, expected);
  }
 
  #[test]
  fn ignore_whitespace_in_string() {
  let input = "\" hallo \"";
- let expected = "\" hallo \"\n";
- run_test(input, expected);
- }
-
- #[test]
- fn add_new_line() {
- let input = "null";
- let expected = "null\n";
+ let expected = input;
  run_test(input, expected);
  }
 
@@ -131,7 +124,7 @@ myfunc(one)
  #[test]
  fn remove_leading_whitespace() {
  let input = " 0";
- let expected = "0\n";
+ let expected = "0";
  run_test(input, expected);
  }
 }