client.config read spmrc by default

destination in client.install use spmrc.get('install.path') fix #15
use inherits@1.0.0 fix tar pack
Merge pull request #17 from afc163/master

never allow some ignore files
Merge pull request #16 from spmjs/spmrc

client.config read spmrc by default
use spy instead
Merge pull request #18 from spmjs/spy

use spy instead
bump 0.2.3
typo fix
improve debug when server error
Merge branch 'master' of github.com:spmjs/spm-client
more info in install error, fix #20