Add pester

Pester provides a framework for running Unit Tests to execute and
validate PowerShell commands inside of PowerShell.

pester.json

@@ -0,0 +1,25 @@
+{
+    "version":  "3.3.6",
+    "license":  "https://raw.githubusercontent.com/pester/Pester/master/LICENSE",
+    "url":  "https://github.com/pester/pester/archive/3.3.6.tar.gz",
+    "homepage":  "https://github.com/pester/Pester",
+    "hash":  "38a9ae3c829b02fe90fb8acbed564ffb883fb0175a6a00b501ac3663f03d6b9a",
+    "extract_dir": "pester-3.3.6",
+    "bin": "bin\\pester.bat",
+    "post_install": " 
+        if(!(test-path $profile)) {
+            $profile_dir = split-path $profile
+            if(!(test-path $profile_dir)) { mkdir $profile_dir > $null } 
+            '' > $profile
+        }
+
+        $import = \"try { `$null = gcm pester -ea stop; import-module `\"$dir\\pester.psm1`\" } catch { }\"
+        $text = get-content $profile
+        if (($text | sls 'pester') -eq $null) {
+            $new_profile = @($text) + $import
+            $new_profile > $profile
+        }
+
+        iex \"$import\"
+    "
+}