add StringSlice func

Merge pull request #14 from ieee0824/string-slice

add test

stable version

v1.0.0

Update README.jp.md

Dump output of environment variables.

You can output by setting GETENV_DUMP_MODE in the environment variable.

v0.2

add type

• int32
• int64
• int16

v0.1

Parse Unix env

• int
• Bool
• string
• time.Duration