Removes encode_unicode as a dependency of rustyline

Remove_encode_unicode.diff

commit 16e951e0e7275500d2d27c9431a7a9d6e41b6ad9
Author: Torbjørn Birch Moltu <t.b.moltu@lyse.net>
Date:   Tue Jun 20 16:50:30 2017 +0200

    Remove encode_unicode dependency
    
    This bumps the minimum version of Rust from 1.12 to 1.15
    and is therefore a breaking change.

diff --git a/.travis.yml b/.travis.yml
index 76221a4..80745d1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,6 @@
 language: rust
 rust:
-  - 1.12.0
+  - 1.15.1
   - beta
   - nightly
 script:
diff --git a/Cargo.toml b/Cargo.toml
index 278b223..76fa9fe 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,7 +12,6 @@ license = "MIT"
 [dependencies]
 libc = "0.2.7"
 unicode-width = "0.1.3"
-encode_unicode = "0.1.3"
 
 [target.'cfg(unix)'.dependencies]
 nix = "0.7"
diff --git a/src/lib.rs b/src/lib.rs
index 8143fc2..788b0b6 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -20,7 +20,6 @@ extern crate libc;
 #[cfg(unix)]
 extern crate nix;
 extern crate unicode_width;
-extern crate encode_unicode;
 #[cfg(windows)]
 extern crate winapi;
 #[cfg(windows)]
@@ -45,7 +44,6 @@ use std::path::Path;
 use std::result;
 use tty::{RawMode, RawReader, Terminal, Term};
 
-use encode_unicode::CharExt;
 use completion::{Completer, longest_common_prefix};
 use consts::KeyPress;
 use history::{Direction, History};
@@ -297,7 +295,8 @@ fn edit_insert(s: &mut State, ch: char) -> Result<()> {
                 // Avoid a full update of the line in the trivial case.
                 let cursor = calculate_position(&s.line[..s.line.pos()], s.prompt_size, s.cols);
                 s.cursor = cursor;
-                write_and_flush(s.out, ch.to_utf8().as_bytes())
+                let mut buf = [0u8; 4];
+                write_and_flush(s.out, ch.encode_utf8(&mut buf).as_bytes())
             } else {
                 s.refresh_line()
             }