In an effort of ensuring consistent code style in test files as with
the "production" source code, we should run eslint as part of the
`$ npm test` script as well.

Most of the related fixes was done by `eslint` using the `--fix` argument.

Only special configuration tweaks for tests compared to the other
source code, is to allow functions declaration without names. The
rationale for allowing that in tests, is that the important reason we
have them in the source code (proper stacktraces) aren't as important
in test files.

Fixes this failure:

      1) Mustache CLI without partials writes rendered template into the file specified by the third argument:
         Uncaught TypeError [ERR_INVALID_CALLBACK]: Callback must be a function
          at makeCallback (fs.js:136:11)
          at Object.unlink (fs.js:943:14)
          at test/cli-test.js:86:12
          at ChildProcess.exithandler (child_process.js:285:7)
          at maybeClose (internal/child_process.js:982:16)
          at Process.ChildProcess._handle.onexit (internal/child_process.js:259:5)

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

* Fixes CLI tests for windows

* Hijacked exec so we don't have to wrap each command in changeForOS, and made replacing 'cat' safer with word boundaries

* Fixing changed tests to be more consistent with the code base

Fixes #431

CLI used to render a mustache template with a data view, writes the template into stdout when successfull. Otherwise meaningfull errors into stderr.

Fixes #424