ERROR-log on symbolic links

filepath.Walk does not follow symbolic links.
There's no easy fix for that outside of Go, so the best we can do for now is to give notice to the end user by ERROR log statements.

This commit also fixes a related panic situation in GenerateTemplateNameFrom when the layout dir was a symbolic link.

Fixes #283
Make Urls in menus respect CanonifyUrls

Fixes #519
Revert "Make Urls in menus respect CanonifyUrls"

This reverts commit 3ccb3979028aafb3e6cc16d47daa77a1fdea11fa.
Commented commands package
Commenting helpers package
Trigger an editor after `hugo new`.

- Trigger permanently with NewContentEditor in config.{toml,yaml,json}.
- Trigger on an individual basis with --editor.
Use current working dir as WorkingDir instead of hugo executable's dir
Trigger an editor after `hugo new`.

- Trigger permanently with NewContentEditor in config.{toml,yaml,json}.
- Trigger on an individual basis with --editor.
Use current working dir as WorkingDir instead of hugo executable's dir
Commented helpers package
Merge branch 'master' of github.com:spf13/hugo
Add configuration option 'Title404'

Allow 'Title404' to be set for the title of the 404 page in config.*.