Enable to change root path

[deadcheat]

what

for example,

real path:
/tmp/assets/images/example.png

virtual path:
/images/example.png

specified on command line: awsset -base / /tmp/assets/images

or
/statics/images/example.png

specified on command line: awsset -base /statics /tmp/assets/images

how

1. separate base path from specified path( if path is /tmp/assets/images, base name is images)
2. join base path and specified path