We added the `--all` flag (now renamed to `--eval-all`) for various
commands for this behaviour so let's start deprecating this.
Also, introduce a `HOMEBREW_EVAL_ALL` environment variable to use the
existing, less secure, behaviour by default and avoid passing
`--eval-all` everywhere.
- This also required auto-fixes for Layout/EmptyLinesAroundBlockBody and
Layout/InconsistentIndentation once the auto-fixer had got rid of the
"redundant begin"s.
I benchmarked these both locally and neither use of `Thread.new`
provides any measurable speedup (and in the `readall` case appears to
slow things down) on my 8 core machine.
* readall: move readall logic to new class.
* tap: run readall when tapping.
This will prevent tapping an tap with syntax errors from causing issues
for users.
Fixes#58.
