Enhanced the LexerError and Documentation of Types

I went and enhanced the LexerError to now wrap a Rust source Error.
This makes it so we can wrapup the possible IO errors we get when trying
to open a file and read its contents.

I also added some documentation for all the implemented functions.

src/lexer.rs

@@ -72,13 +72,12 @@ impl Lexer
       let mut cursor = Position::default();
       let mut stream = TokenStream::new();
 
-      let input_file = File::open(&path).map_err(|_error| {
+      let input_file = File::open(&path).map_err(|err| {
                                            LexerError::new(
-                "Unable to open file for Lexigraphical Analysis.",
+                "Unable to open file for Lexical Analysis.",
                 Span::default(),
-                Some(path.as_ref().to_string_lossy().to_string()),
-                None,
-            )
+                Some(path.as_ref().to_path_buf()),
+                None).with_source(err)
                                         })?;
 
       let reader = BufReader::with_capacity(BUFFER_SIZE, input_file);
@@ -138,7 +137,8 @@ impl Lexer
    }
 
    /// Internal: scans a single line of text into tokens.
-   fn scan(line: &str, stream: &mut TokenStream<TokenType>, cursor: &mut Position)
+   fn scan(line: &str, stream: &mut TokenStream<TokenType>,
+           cursor: &mut Position)
    {
       for c in line.chars()
       {