* fix: add upgrade and branch timings to log

Adds timing logs for upgrade detection + branch updating stages.

Closes #821

* improve request retry logging

`npm` and `yarn` lockfile generation use promisified child process `exec` now instead of `spawnSync`.

This fix improves the way Renovate detects embedded/installed npm and yarn. It tries:
- locally installed npm or yarn
- npm or yarn embedded inside globally installed renovate
- globally installed npm or yarn
- global `yarn` or `npm` commands as fallback

Fixes #824 

* chore(deps): update dependency prettier to v1.6.1

* chore(deps): update dependency prettier to v1.7.0

* run lint

* chore(deps): update dependency eslint-config-airbnb-base to v12.0.0

* fix lint

* install npm from npm

* use embedded npm and remove versions checking

Renovate will now depend on yarn like any other dependency and call this version directly, instead of having an embedded version. This will allow us to "renovate" the yarn version we use too.

* fix eslint configuration

* run eslint fix

* add minimatch

* feat: use package names for ignoring when lerna or workspaces

Renovate will now:
- Find all package.json files matching lerna or yarn workspaces glob pattern
- Retrieve package names from within those package.json files
- Implicitly ignore (not renvoate) any of those names

Closes #781

* remove registry-url

* replace registry-url with registry-auth-token

Fixes #793

This is a major refactor of branch code to prepare for Yarn workspaces plus creating PRs for branches with failing lockfiles. Marked as "feature" to cause a minor version bump due to the moderate chance of accidentally breaking something.

Eliminating one more possibility for #707

tmpDir is now created once per-repository and package.json files are written and lockfiles generated based on the repo's directory structure. This way node_modules can be reused between branches in same run.

Closes #501