Fixes invalid value for ddl-auto in sagan-site

Change spring.jpa.hibernate.ddl-auto from 'false' (invalid) to 'none' in sagan-site. This was previously fixed in sagan-indexer (see #365), but missed this one.
Attempt to add Disqus comment count

Per instructions at http://help.disqus.com/customer/portal/articles/565624
Remove #disqus_thread from href
Assign value of ${post.id} to data-disqus-identifier
Use protocol-relative URL syntax to fetch Disqus JS
Add css to show comment icon on blog index page

Also, updated iconsprite with latest version which includes the icon
itself.
Add comment count to blog post page
Merge pull request #383 from bjornerik/fix-ddl-auto2

Fixes invalid value for ddl-auto in sagan-site
Merge pull request #339 from spring-io/comment-count
Update tests to reflect GitHub's new path to raw content

The dynamic sidebar tests use macros, which are located on github via
raw URLs. When they changed their path, it didn't cause any failures
while also slowing down the tests (see #369).

This commit updates the tests to use the new paths and also added a
check to verify that macro content was actually loaded. Both should
cause a more recognizable failure if github makes similar edits.

The impact is that all the guides need to be updated to reflect the new
paths.
Ignore DynamicSidebarTests

Related to #369 and #379, this commit comments out DynamicSidebarTests
until we're able to figure out and solve whatever problem is causing
them to execute so slowly (on the order of 30 seconds--unacceptable for
any unit test).
Modify and merge pull request #379 from gregturn/github-raw-content-moves

Changes from original pull request:

 - Added commit ignoring DynamicSidebarTests, as they remain extremely
   slow even after the changes in this PR.

 - Reformatted commit comments for style.

Resolves #379
Add Spring Cloud as a project

* add project icon in icon sprite
* add project description in the projects page
Merge pull request #385 from bclozel/sagan-385

Add spring-cloud project
Add db migration file for Spring Cloud