修改PS1变量

PS1='[e[7;46m]u[e[0m]@[e[0;32m]h[e[0m]:[e[0;34m]w[e[0m]$ '
新的比较好的变量：

PS1='[e[7;36m]u[e[0m]@[e[0;32m]h[e[0m]:[e[0;34m]W[e[0m]$ '

ref from:

http://professor.blog.51cto.com/996189/1572141

http://www.cnblogs.com/jsfans/p/3844779.html