Add an `install` target to Makefile.
Add timezone to buildDate
Fix various Windows-issues

File handling was broken on Windows. This commit contains a revision of the path handling with separation of file paths and urls where needed.

There may be remaining issues and there may be better ways to do this, but it is easier to start that refactoring job with a set of passing tests.

Fixes #687
Fixes #660
Trigger an editor after `hugo new`.

- Trigger permanently with NewContentEditor in config.{toml,yaml,json}.
- Trigger on an individual basis with --editor.