Update docs

docs/centos-installation.markdown

@@ -34,6 +34,8 @@ If SeLinux is enabled, be sure that the Apache user can write to the directory d
 chcon -R -t httpd_sys_content_rw_t /var/www/html/kanboard/data
 ```
 
+Be sure to configure your server to allow Kanboard to send emails and make external HTTP requests.
+
 You can also disable SeLinux if you don't need it.
 
 Centos 6.5

docs/email-configuration.markdown

@@ -93,3 +93,4 @@ If no emails are send and you are sure that everything is configured correctly:
 - Check your spam folder
 - Enable the debug mode and check the debug file `data/debug.log`, you should see the exact error
 - Be sure that your server or your hosting provider allow you to send emails
+- If you use SeLinux, allow PHP to send emails

docs/faq.markdown

@@ -21,12 +21,22 @@ Kanboard have been tested on the following devices:
 - Mozilla Firefox
 - Safari
 - Google Chrome
-- Internet Explorer > 10
+- Internet Explorer 11
 
 ### Tablets
 
 - iPad (iOS)
-- Nexus 7 (Android)
+- Nexus 7 (Android/Chrome)
+
+
+I get a blank page after installing or upgrading Kanboard
+---------------------------------------------------------
+
+- Check if you have installed all requirements on your server
+- Check if the files have the correct permissions
+- If you use php-fpm and opcode caching, reload the process to be sure to clear the cache
+- Enable PHP error logging in your php.ini
+- Check the PHP and Apache error logs you should see the exact error
 
 
 Known issues with eAccelerator
@@ -94,5 +104,6 @@ There is a [package to install Kanboard on Yunohost easily](https://github.com/m
 
 
 Are there some tutorials about Kanboard in other languages?
-------------------------------------
- - [German article series about Kanboard](http://demaya.de/wp/2014/07/kanboard-eine-jira-alternative-im-detail-installation/)
+-----------------------------------------------------------
+
+- [German article series about Kanboard](http://demaya.de/wp/2014/07/kanboard-eine-jira-alternative-im-detail-installation/)

docs/installation.markdown

@@ -6,7 +6,7 @@ Requirements
 
 - Apache or Nginx
 - PHP >= 5.3.7
-- PHP extensions required: mbstring and pdo_sqlite (don't forget to enable extensions)
+- PHP extensions required: mbstring, gd and pdo_sqlite (don't forget to enable extensions)
 - A modern web browser
 
 From the archive (stable version)