Fix ReadFile function
Change destination directory rebuild rule
Add layout fields for content or body
Handle errors when loading includes and layouts
Disable escapes on templates

The input is assumed to be solely
given by the site creator and therefore
safe.
Fix path on env
Allow verbatim copies of files
Fix funcMap scope
Refactor finding of env range
Fix trimming of source path
Rename env functions
Add build command line option
Move test util function to a separate package

Importing testing package spams the
command line options with test flags.
Add clean command line option