Look for plugins under the source directory

When generating the site, Jekyll will now look for plugins under the
source directory by default. The plugin location can still be changed in
_config.yml
Merge remote-tracking branch 'upstream/master' into issue-653
Look for plugins under the source directory by default
Add TomDoc
Merge branch 'master' into issue-653
Improve error message for malformed highlight tags
Added the --future switch back to the CLI
Added in --limit-posts
Cleaner output when generating site.
Improved output for auto-regeneration.
Reworking errors with configuration file.
Updating tests for new config output.
Allow symlinked folders in unsafe mode
Now uses the more semantically correct AND operator
Upgrading to safe_yaml v0.7
Safe loading of files and YAML.
Updating tests for safe_yaml.
Relax Kramdown version to 0.14. Fixes #808.
Merge pull request #807 from mojombo/safeyaml-warnings

Fix SafeYAML Warnings
Update history to reflect merge of #807.