Remove unneeded files from packaged builds (#642)

* Remove unused files from packaged builds

* Update package.json postinstall steps

* More npm install fixes

* Colorizer test fix

* Clean-up typescript module

* Fix yarn build on macOS

* Add gulp to dev dependencies

* Fix macOS build

build/npm/postinstall.js

@@ -25,12 +25,10 @@ yarnInstall('dataprotocol-client');
 yarnInstall('extensions-modules');
 yarnInstall('extensions'); // node modules shared by all extensions
 
-yarnInstall('extensions'); // node modules shared by all extensions
-
 const extensions = [
 	'vscode-colorize-tests',
 	'json',
-  'mssql',
+    'mssql',
 	'configuration-editing',
 	'extension-editing',
 	'markdown',
@@ -38,7 +36,6 @@ const extensions = [
 	'merge-conflict',
 	'insights-default',
 	'account-provider-azure'
-
 ];
 
 extensions.forEach(extension => yarnInstall(`extensions/${extension}`));