minor #273 Added a "troubleshooting" section in the README to solve common issues (javiereguiluz)

This PR was merged into the 1.0-dev branch.

Discussion
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Added a "troubleshooting" section in the README to solve common issues

This could help us mitigate the SSL issues on Windows while we solve them.

The contents were inspired by this section of the Humbug project by @padraic: https://github.com/padraic/humbug#self-update-request-debugging

Commits
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4f13371 Added a "troubleshooting" section in the README to solve common issues

Author: javiereguiluz

README.md

@@ -129,3 +129,29 @@ c:\> php symfony self-update
 > installer tries to guess the best proxy settings from the `HTTP_PROXY` and
 > `http_proxy` environment variables. Make sure any of them is set before
 > executing the Symfony Installer.
+
+Troubleshooting
+---------------
+
+### SSL and certificates issues on Windows systems
+
+If you experience any error related with SSL or security certificates when using
+the Symfony Installer on Windows systems:
+
+1) Check that the OpenSSL extension is enabled in your `php.ini` configuration:
+
+```ini
+; make sure that the following line is uncommented
+extension=php_openssl.dll
+```
+
+2) Check that the path to the file that contains the security certificates
+exists and is defined in `php.ini`:
+
+```ini
+openssl.cafile=C:/path/to/cacert.pem
+```
+
+If you can't locate the `cacert.pem` file anywhere on your system, you can
+safely download it from the official website of the cURL project:
+http://curl.haxx.se/ca/cacert.pem