Changed postgresql note

Also made yarn a mandatory installation process.

Some corrections

Removed some redudant troubleshooting options

doc/howto/troubleshooting.md

@@ -360,20 +360,10 @@ RAILS_ENV=test bundle exec rake db:reset
 * `gdk run db` fails with exit code X
-    If you have restarted your computer recently don't forget to start the postgresql service manually, init.d scripts don't currently as of build 15063.138
-
-    TL;DR
+    If you have restarted your computer recently, don't forget to start PostgreSQL server manually; init.d scripts don't work currently as of build 15063.138:
     `sudo service postgresql start`
-* `gdk run app` fails with gitaly error code XXX
-
-    Please run `gdk reconfigure`, note, this *might* happen during the initial run after the database has seeded
-
-* I get an EOF when accessing http://127.0.0.1:3000 instead of the sign up page
-
-    There's two possible solutions for this problem, make sure you have sufficient free RAM, otherwise just refresh the page.
-
 ## Other problems
 Please open an issue on the [GDK issue tracker](https://gitlab.com/gitlab-org/gitlab-development-kit/issues).

doc/prepare.md

@@ -186,16 +186,14 @@ redis go node icu krb5 phantomjs gmake
 ### **Experimental** Windows 10 using the WSL (Windows Subsystem for Linux)
-Install node from source
+Install NodeJS from source
 ```
 curl -O https://nodejs.org/dist/v6.10.2/node-v6.10.2.tar.gz
 tar -zxf node-v6.10.2.tar.gz
 cd node-v6.10.2
 ```
-follow the instructions inside the BUILDING.md document
-
-TL;DR BUILDING.md
+Build the NodeJS library. The following instructions are copied from the NodeJS BUILDING.md document:
 ```
 sudo apt-get install build-essential
@@ -211,7 +209,7 @@ rvm install 2.3.3
 rvm use 2.3.3
 ```
-Install yarn *Recommended but it can be skipped*
+Install yarn
 ```
 curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
@@ -230,7 +228,7 @@ sudo apt-get install git postgresql postgresql-contrib libpq-dev redis-server li
 sudo npm install phantomjs-prebuilt@2.1.12 -g
 ```
-Once the prerequisites have been installed don't forget to start the postgresql manually otherwise the gdk installation will fail
+Start the PostgreSQL database
 ```
 sudo service postgresql start