Thanks @hbetts aka @destroyerofbuilds for your continued contributions to the project.

docs: Improve local development information

Closes: #1586

Signed-off-by: Adam Moss <adam.moss@bcs.org.uk>

docs(contributing): fix typo

This reverts commit 81c72247.

Re-enables branch cleanup for multiple baseBranches

Remove outdated packageFiles description

Adds initial support for `.nvmrc` renovation. If the existing value is a fully-specified semver version then it will be upgraded, otherwise left alone.

Closes #1270 

This reverts commit c6be3154.

Closes #1584

Retains the "node" configuration object but moves enabling/disabling to "travis". Also removes the default `supportPolicy` from config.

Updates travis config and logic to use same variables as for other managers. This fixes the onboarding PR.

Fixes #1551

Refactors all non-npm code to live inside lib/manager/*

A semver range defining allowed versions for dependencies

| name | value  |
| ---- | ------ |
| type | string |

Use this - usually within a packageRule - to limit how far to upgrade a dependency. For example, if you wish to upgrade to angular v1.5 but not to `angular` v1.6 or higher, you could defined this to be `<= 1.5` or `< 1.6.0`:

```
  "packageRules": [{
    "packageNames": ["angular"],
    "allowedVersions": "<=1.5"
  }]
```