remove old syntax flag from gitignore, add nanoc crash

The NO_SYTNAX flag was around when we were using older rendering
methods and it slowed down the local compile. No longer needed as of

When `nanoc check` is run, it outputs a local crash log. No need to
commit that.
remove commented out nanoc rake tasks

The nanoc cli command is the preferred interface for running external
tasks. All rake commands that use it will alert the operator to do so.
remove a few unneeded dependencies

- asdf: probably for browser functions, replaced by rack and guard
- mime-types: probably for the same reason, when we serving this as a live site
- systemu: can't find a reason for this one. Might have been used in Rake tasks output
- timers: still used, but pulled in by celluloid. We don't need to specify it.
update nokogiri and mini_portile for security

CVE-2013-6460 & CVE-2013-6460 - memory exhaustion when using JRuby.
Not something we really need to worry about, but a good idea to remain patched.
Merge pull request #262 from DataDog/miketheman/bundle

Dep updates