Up version
Changes for v0.5.1
Fixed file name substitution

- Remove dots from file names that are resolved from other properties
- Don't lower case file names that are not resolved from other properties
JSON: Allow newlines and indentation in strings
JSON: Resolve multiple placeholders in a single property
Drafts

- New items are not added to the meta file by default
- New items have their timestamps set to 'DRAFT'
- The formatted dates are all set to 'DRAFT' for items with a created
  timestamp of 'DRAFT'
- Passing the command line option --publish sets the timestamps of new
  items to now and adds the item to the meta file
Made --force obsolete

- Always rendering all HTML content
- Comparing rendered files with content in site directory
- Removed --forced option handling
Introduce 'publish' flag available to all sites

When running 'blogdown --publish' the flag is set to true, otherwise
false.
Only persist blogdown.meta when publishing