Lints and watches

[svi3c]

This PR adds linting for styles via stylelint. Also the linter are run on file changes.

Resolves #24 Resolves #23

@DorianGrey

[DorianGrey]

Hm... I see several issues here:

• The tasks started by the watcher are not as silent as they should be. A failed lint is followed by a "regular" NPM error message (causing the creation of an npm-debug.log). which makes the lint errors hard to find and read on the terminal.
• Changing multiple files of the same watched category and save them at once causes the linting tasks to be started once per saved file. This is definitely ineffective. There should be some kind of "debounce" before they are executed. While npm-watch does not seem to support this (yet), the underlying nodemon offers a delay flag.
• Always linting all related files just because a few of them changed is somewhat... ineffective. Linting should only be executed on changed files.

The latter two issues might especially causes problems in larger projects.

[svi3c]

@DorianGrey you are absolutely right! It was just simple to use the CLI. I'll give the linting API a try and use chokidar for change detection and batch the linting for the changed files. Since the linting does not have to check any dependencies, we should be able to lint only the changed files.

[svi3c]

@DorianGrey I just updated the stuff. Please re-check. The linting is very quick now. We keep the errors in memory and update them incrementally. This way we can show all linting errors, even if only one file changed. I think this is better than having only the linting errors for the currently modified file, since there is some output in the dev console which scrolls the older errors out of sight.

[DorianGrey]

I agree - that's one of the problems which regularly occur on most build tools.

But there is on thing that should be added to this PR as well: we've currently restricted the node engine version to >= 4.0.0. Trying to use this version causes a warning:

npm WARN engine stylelint@7.1.0: wanted: {"node":">=4.2.1"} (current: {"node":"4.0.0","npm":"2.14.2"})

The engine restriction should be raised to something like (NPM > 3 should be preferred over 2.x anyway):

"engines": {
  "node": ">=4.5",
  "npm": ">=3.9"
}

Otherwise, things might fail to work in several circumstances - I don't think the styleline-devs set this restriction for no reason. Maybe providing a .nvmrc would be useful as well.

Another warning that (curiously) only occurred when using 4.0.0 was this:

npm WARN package.json Dependency 'http-proxy' exists in both dependencies and devDependencies, using 'http-proxy@^1.14.0' from dependencies

Which holds true. I'm wondering why NPM 3.10 did not complain about this lately, but we should try to avoid this warning anyway.

[svi3c]

Okay, done :)

[DorianGrey]

I've reverted the change to the zone.js dependency and added the commit to this branch. Suppose this change happend by accident (caused by jspm install - happend to me as well...). W.r.t. its issue list, we should not allow a variable range for this dependency for now. E.g. https://github.com/angular/zone.js/issues/407 - I've also seen this while updating dependencies for RC.5 and reverted to 0.6.12.

Everything else looks fine and will be merged once Travis is ready.

€dit: I've update the .travis.yml as well, to match the changed engine restrictions.