Update crate to fix compile error

Cargo.toml

@@ -15,7 +15,7 @@ multiboot2 = "0.1.0"
 bitflags = "0.7.0"
 x86_64 = "0.1.2"
 once = "0.3.3"
-linked_list_allocator = "0.4.2"
+linked_list_allocator = "0.5.0"
 
 [dependencies.lazy_static]
 version = "0.2.4"

README.md

@@ -1,5 +1,7 @@
 # RustOS for x86_64 SMP
 
+[![Build Status](https://travis-ci.org/wangrunji0408/RustOS.svg?branch=master)](https://travis-ci.org/wangrunji0408/RustOS)
+
 A project of THU OS2018 spring.
 
 [Project Wiki](http://os.cs.tsinghua.edu.cn/oscourse/OS2018spring/projects/g11)