Resolve the babel rc relative to the file path, not the CWD Fixes babel#252

* REMOVE webpack devDependency as we have multiple peerDep versions
* Add matrix testing against supported node & webpack versions
* Enable codecov.io reporting
* Add travis script for test and coverage
* Rename cov script to cover to take advantage of `postcover`
* Add postcover script for travis linting after testing
* Temporarily allows failures on `OSX` ( timeout on node4 )

* add babel-core and preset-2015 to dev dependencies

currently it is impossible to run tests after forking the `babel-loader` without installing "babel-core" and "babel-preset-2015"
adding them to the dev-dependencies will fix this. (I saw the dependencies as they are installed in the "before_script" according to the .travis.yml

* no longer install `babel-core` and `babel-preset-es2015` in travis

this is now done on npm install as they are devDependencies, so installing them again is redundant

* Hide stack trace (shown only when detailed error reporting is enabled in
  webpack)
* Strip filename (already reported by webpack in a more concise format).

typo

Legal makes it sounds like it's a legal issue, yet it's more about the validity of the value.

https://greenkeeper.io/

Set the default cache directory as the
[common cache directory](https://github.com/avajs/find-cache-dir),
`./node_modules/.cache/babel-loader`.

Previously, when `cacheDirectory` was set to `true`, babel-loader
tried to use the operating system's temporary directory as a cache
directory.

However, when running npm scripts as the root user,
[npm overrides the TMPDIR environment variable](npm/npm#4531).
This caused the cache files to be created in the project folder itself,
for example when using Docker: facebook/create-react-app#483.

…#317)

move lib to src and have lib the destination of babel

* Use eslint and nyc

* migrate to jest

* Use ava

* fix prefer-const

* improve sourceFileName gennerate logic with new relative method

* add test for relative method

webpck 2.1.0-beta.26 does not support shorthand loader names

* updates docs re: transform-runtime

* moves polyfill message to follow transform-runtime

* Correct link to regenerator

* Changelog 6.2.8

* Update Changelog [skip ci]

* Update CHANGELOG.md

* Update dev dependencies

* Update webpack and remove tests that have no effect with webpack 2

- add metadataSubscribers option as an array of context functions to call
- pass metadata to metadataSubscribers functions
- add section about cacheDirectory ENOENT error to README.md