kiln 0.4.0

kiln 0.4.0 brings many new features and improvements:

- Support for site-wide base templates
- Support for symlinks in the templates directory
- Support for per-page templates specified in frontmatter
- Permalinks are now configured per-task

Adnan Maolood (7):
      templates/_default/atom.xml: Add required links
      Simplify error handling for static content
      Show the task for which the error occured
      page: Don't fallback to base template
      templates: Fix base template block customization
      Implement support for per-page templates
      site: Configure permalinks per task

Duncan Bayne (1):
      Display detailed error message on static build failure

Edd Salkield (5):
      templates.go: Resolve symlinks
      templates.go: Support default base templates
      docs: Update template-related documentation
      page.go: report error in template override failure
      docs: Update frontmatter template override documentation