Use bash code blocks for git stuff
Fix pretty url filter
Added one more missing bash syntax instance.
Added link to Amazon integration
Synched integration sidebar and placeholder pages.
Use different IDs for stock items and stock locations in stock items guide

Fixes #139
Changed "Overview" links to "Terminology"
Added use of $ for bash commands to readme & contributing guide
Standardized bash $ format on examples in readme/contributing
Standardized bash $ syntax on several guides.
Added links to the sample code files.
Remove legacy source directory which is not used by nanoc
Added new filter to make TODO content blocks easier to spot
Started work on message basics
Fix message
A few spelling corrections, one minor sample code fix.
Merge branch 'master' of github.com:spree/spree-guides

Conflicts:
	content/integration/message_basics.md
Add --- filter for adding filenames to code examples
More progress on message basics
Style section title icons