Made `git clone` optional for instructions

CUSTOMIZATION.md: Fix 'administraotrs' -> 'administrators' typo

This snuck in with 48c5eda1 (Updating note on customization,
2015-01-21, #138).

Added note on installing Jekyll with specific version of Ruby

This reverts commit 8d0905be.

Minor typo fix.

Link directly to Windows Installer repo for executable

To avoid the manual step of emailing and uploading new releases of the
Windows Installer this moves to downloading the file directly from the GitHub
release and updating the associated link in _config.yml.

index: Add HTML IDs to sections that lacked them

added survey to config.yml edit index.html links

Meta tags

"join" filter only works on lists (arrays), so when `instructor`
or `helper` are strings (or empty objects) then the result will be "".

But when they are arrays of strings, then the result will be like:
"Piotr Banaszkiewicz|Greg Wilson".

People can be named "John Smith, Jr.", but (probably) not
"John Smith| Jr."

I missed anchors for linking to the syllabus today.  The "syllabus-"
prefix avoids colliding with the existing setup IDs
(e.g. "syllabus-shell" for the syllabus entry and "shell" for the
setup entry).

added pre/post survey links

These are rarely used in SWC workshops, and many instructors are
pointing their students at these installation-test scripts without
customizing CHECKS first.  Until we get an easier way to configure the
checks, just make the default settings a bit more relaxed.

Capitalize Bash in installation instructions for Mac

The installation instructions for Mac OS X had
"bash", change this to "Bash".

Added new FAQ

Update link of Etherpad to http://pad.software-carpentry.org

Improve Git installation instructions on Windows

Update instructions to download Anaconda