Remove 'not found in _includes' hacks

Remove the use if "unless contains 'not found in _includes directory'"
hacks that were previously used to detect when _includes were missing.

This change is required as the hack no longer works with the latest
Jekyll release (and therefore also with GitHub).

Additional 'custom_pom_template' and 'custom_gradle_template' flags
must now be set in _config.yml if you want to include a custom pom.xml
or build.gradle file.
Add missing ZeroClipbpard SWF file

Flash support for ZeroClipboard is not working in project pages since
the SWF file is missing. There was a typo in the .gitignore file that
ignored "*.sw?" files.
Make the link to a project's forum optional

Omit the link to the forum if the project's metadata does not provide
a forum url
Merge pull request #5 from wilkinsona/optional-forum-link

Make the link to a project's forum optional
Merge pull request #4 from bclozel/zclip

Fix ZeroClipboard integration in gh-pages
Change Forum navbar item to Questions

The projects navbar should mirror the one on the spring.io website.
Merge pull request #7 from bclozel/forum

Update navbar item "Forum" -> "Questions"
Fix company name and website in footer
Fix "rm -rf" instruictions

Existing copy is wrong because "git rm -rf *" fails if there are any untracked files (e.g. target/). Changed to "git rm -rf `git ls-files`".
Merge pull request #8 from dsyer/patch-1

Fix "rm -rf" instruictions
Gem installation instructions updated

Using "gem install" didn't work for me because of the Gemfile.lock that is in source control (presumably for a reason).
Fix directory name for sample pages
Merge pull request #10 from dsyer/patch-3

Fix directory name for sample pages
Add "gem install bundler" for people using vanilla Ruby
Merge pull request #9 from dsyer/patch-2

Gem installation instructions updated
Merge remote-tracking branch 'gh-pages-upstream/gh-pages' into gh-pages