feat: use npm's config system

BREAKING CHANGE:

`rc` is not used to get configs.

BREAKING CHANGE:

`.pnpmrc` files are ignored

BREAKING CHANGE:

configs in json format are not supported

BREAKING CHANGE:

`--config` argument renamed to `--userconfig`

Close #696, Close #40

package.json

@@ -20,6 +20,8 @@
     "@types/load-json-file": "^2.0.5",
     "@types/mz": "^0.0.31",
     "@types/node": "^7.0.5",
+    "@types/nopt": "^3.0.29",
+    "@types/npm": "^2.0.28",
     "@types/ramda": "^0.0.7",
     "@types/rc": "^0.0.1",
     "@types/semver": "^5.3.30",
@@ -29,7 +31,7 @@
     "arr-flatten": "^1.0.1",
     "bole": "^3.0.2",
     "byline": "^5.0.0",
-    "camelcase-keys": "^4.0.0",
+    "camelcase": "^4.1.0",
     "common-tags": "^1.4.0",
     "cross-spawn": "^5.0.0",
     "execa": "^0.6.3",
@@ -46,13 +48,14 @@
     "load-yaml-file": "^0.1.0",
     "loud-rejection": "^1.6.0",
     "mem": "^1.1.0",
-    "meow": "^3.7.0",
     "mkdirp-promise": "^5.0.1",
     "mz": "^2.6.0",
     "ndjson": "^1.5.0",
     "node-gyp": "^3.6.0",
+    "nopt": "^4.0.1",
     "normalize-path": "^2.1.1",
     "normalize-ssh": "^1.0.0",
+    "npm": "^4.5.0",
     "npm-package-arg": "^5.0.0",
     "npm-registry-client": "^8.1.0",
     "os-homedir": "^1.0.2",
@@ -68,11 +71,9 @@
     "pnpm-logger": "^0.3.0",
     "proper-lockfile": "^2.0.0",
     "ramda": "^0.23.0",
-    "rc": "^1.2.0",
     "read-pkg": "^2.0.0",
     "read-pkg-up": "^2.0.0",
-    "registry-auth-token": "^3.1.0",
-    "registry-url": "^3.1.0",
+    "registry-auth-token": "^3.2.0",
     "remove-all-except-outer-links": "^1.0.0",
     "rimraf-then": "^1.0.1",
     "semver": "^5.3.0",