Implement testing using Pester

Integrate with AppVeyor

pester.json

@@ -7,19 +7,26 @@
     "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
-        }
 
+        if($profile) {
+            'adding pester to powershell profile...'
+            if(!(test-path $profile)) {
+                'powershell profile doesn''t exist. creating...'
+                $profile_dir = split-path $profile
+                if(!(test-path $profile_dir)) { mkdir $profile_dir > $null } 
+                '' > $profile
+            }
+
+            $text = get-content $profile
+            if (($text | sls 'pester') -eq $null) {
+                $new_profile = @($text) + $import
+                $new_profile > $profile
+                success 'pester added to powershell profile.'
+            }
+        } else { warn 'no powershell profile found. the pester module will not be imported each session.' }
+
+        'importing pester for current session...'
         iex \"$import\"
     "
 }