Use SDK r23.0.2
Merge pull request #12 from hanbo/master

Use SDK r23.0.2
Update Readme with references to alternative projects.
Add new option for input file as a list of components

Signed-off-by: Sam Xiao <sam.xs.xiao@gmail.com>
Added NDK download support

Signed-off-by: Sam Xiao <sam.xs.xiao@gmail.com>
Put the SDK/NDK version in an env variable

Signed-off-by: Sam Xiao <sam.xs.xiao@gmail.com>
Fix typo on installing android ndk for mac

Signed-off-by: Sam Xiao <sam.xs.xiao@gmail.com>
Expose ‘PLATFORM_TOOLS_VER’ env variable

Signed-off-by: Sam Xiao <sam.xs.xiao@gmail.com>