add ENV for locale

add ENV["JULIA_LOCALE"], so we could make use of ENV 
```
julia> ENV["JULIA_LOCALE"]="zh_CN"
"zh_CN"

julia> help(sin)
Loading help data...
Base.sin(x)

   计算 "x" 的正弦值，其中 "x" 的单位为弧度。 # This is Chinese ... 

julia> Base.locale("")

julia> help(sin)
Loading help data...
Base.sin(x)

   Compute sine of "x", where "x" is in radians

julia> Base.locale("zh_CN")

julia> help(sin)
Loading help data...
Base.sin(x)

   计算 "x" 的正弦值，其中 "x" 的单位为弧度。

julia>
```