refactor: Remove is

If we expected to receive a barrage of assorted arguments to functions, we might need `is`.

But for Metalsmith, it’s overkill.  People know to pass a string for directories.  People know what a number is.  :P

lib/index.js

@@ -2,7 +2,6 @@
 var assert = require('assert')
 var clone = require('clone')
 var fs = require('co-fs-extra')
-var is = require('is')
 var matter = require('gray-matter')
 var Mode = require('stat-mode')
 var path = require('path')
@@ -25,7 +24,11 @@ rm = thunkify(rm)
  * Helpers
  */
 
-var absolute = function(s) {return path.resolve(s) === s}
+var absolute  = function(s) {return path.resolve(s) === s}
+var isBoolean = function(b) {return typeof b === 'boolean'}
+var isNumber  = function(n) {return typeof n === 'number' && !Number.isNaN(n)}
+var isObject  = function(o) {return o !== null && typeof o === 'object'}
+var isString  = function(s) {return typeof s === 'string'}
 
 
 /**
@@ -75,7 +78,7 @@ Metalsmith.prototype.use = function(plugin){
 
 Metalsmith.prototype.directory = function(directory){
   if (!arguments.length) return path.resolve(this._directory)
-  assert(is.string(directory), 'You must pass a directory path string.')
+  assert(isString(directory), 'You must pass a directory path string.')
   this._directory = directory
   return this
 }
@@ -89,7 +92,7 @@ Metalsmith.prototype.directory = function(directory){
 
 Metalsmith.prototype.metadata = function(metadata){
   if (!arguments.length) return this._metadata
-  assert(is.object(metadata), 'You must pass a metadata object.')
+  assert(isObject(metadata), 'You must pass a metadata object.')
   this._metadata = clone(metadata)
   return this
 }
@@ -103,7 +106,7 @@ Metalsmith.prototype.metadata = function(metadata){
 
 Metalsmith.prototype.source = function(path){
   if (!arguments.length) return this.path(this._source)
-  assert(is.string(path), 'You must pass a source path string.')
+  assert(isString(path), 'You must pass a source path string.')
   this._source = path
   return this
 }
@@ -117,7 +120,7 @@ Metalsmith.prototype.source = function(path){
 
 Metalsmith.prototype.destination = function(path){
   if (!arguments.length) return this.path(this._destination)
-  assert(is.string(path), 'You must pass a destination path string.')
+  assert(isString(path), 'You must pass a destination path string.')
   this._destination = path
   return this
 }
@@ -131,7 +134,7 @@ Metalsmith.prototype.destination = function(path){
 
 Metalsmith.prototype.concurrency = function(max){
   if (!arguments.length) return this._concurrency
-  assert(is.number(max), 'You must pass a number for concurrency.')
+  assert(isNumber(max), 'You must pass a number for concurrency.')
   this._concurrency = max
   return this
 }
@@ -144,7 +147,7 @@ Metalsmith.prototype.concurrency = function(max){
  */
 Metalsmith.prototype.clean = function(clean){
   if (!arguments.length) return this._clean
-  assert(is.boolean(clean), 'You must pass a boolean.')
+  assert(isBoolean(clean), 'You must pass a boolean.')
   this._clean = clean
   return this
 }
@@ -158,7 +161,7 @@ Metalsmith.prototype.clean = function(clean){
 
 Metalsmith.prototype.frontmatter = function(frontmatter){
   if (!arguments.length) return this._frontmatter
-  assert(is.boolean(frontmatter), 'You must pass a boolean.')
+  assert(isBoolean(frontmatter), 'You must pass a boolean.')
   this._frontmatter = frontmatter
   return this
 }

package.json

@@ -26,7 +26,6 @@
     "commander": "^2.6.0",
     "gray-matter": "^2.1.0",
     "has-generators": "^1.0.1",
-    "is": "^3.1.0",
     "is-utf8": "~0.2.0",
     "recursive-readdir": "^2.1.0",
     "rimraf": "^2.2.8",