This was added in #2149 but doesn't support Node < 4

Fix watching of entry points

Currently changes to non-partials are being picked up. This PR Fixes
that and adds addition test coverage.

Fixes #2139

Fix Some Leaks

* Use true-case-path

* Fix failing tests

* Delete package-lock.json

* .gitignore package-lock.json

## Fixes

- Problem with watcher (@evanfuture, #2147)

## Supported Environments

| OS | Architecture | Node |
| --- | --- | --- |
| Windows | x86 & x64 | 0.10, 0.12, 1, 2, 3, 4, 5, 6, 7, 8, 9 |
| OSX | x64 | 0.10, 0.12, 1, 2, 3, 4, 5, 6, 7, 8, 9 |
| Linux* | x86 & x64 | 0.10, 0.12, 1, 2, 3, 4, 5, 6, 7, 8, 9 |
| Alpine | x64 | 4, 6, 7, 8, 9 |
| FreeBSD  10+ | i386 | 4, 6, 8 |
| FreeBSD 10+ | amd64 | 4, 6, 8 |

*Linux support refers to Ubuntu, Debian, and CentOS 5

* gaze.watched returns an object

Since it returns an object, we need to run through the keys, a simple index of isn't enough.  This should fix https://github.com/sass/node-sass/issues/2139

Pointing them to the release notes is safer since it will accurately reflect the support for that version of node-sass

Removed 55 since it was part of a prerelease Node 8 only

Nan::ObjectWrap Docs: https://github.com/nodejs/nan/blob/master/doc/object_wrappers.md#api_nan_object_wrap

Prior to this, all wrapper Objects would never be deleted, allowing memory to grow unbounded.

Example:
The following, would leak WrapperObjects, and never

```
while (true) {
  new sass.types.String(‘I LEAK’);
}
```

* boolean
* function-bridge
* map
* string

Improved the grammar and clarity of the instructions in this project's README

* Remove Node 0.10 and 0.12 from travis config

These will always fails now due to https://github.com/sass/node-sass/issues/2100. We manually verify support when building release binaries so there's no value in failing CI. It's scary to contributors.

* Remove Node 0.10 and 0.12 from appveyor config

These will always fails now due to https://github.com/sass/node-sass/issues/2100. We manually verify support when building release binaries so there's no value in failing CI. It's scary to contributors.

* Link to the troubleshoot guide for Node < 4 installation issues

Help people search for keywords because noone reads the help guides anyway.

Fix a couple of typos and minor Markdown tweaks.

Thanks to @drook for reporting it via #2033

Closes #2027

Fixes #1952
Closes #1956

- fixes issues with transitive dependency scss-tokenizer
- allows graph to follow symlinks

This logic is all tightly coupled in the bin. This logic has been
notoriously impossible to test due to weird fs timing issues. By
extracting the actual logic we're now able to test it in isolation.

With this in place replacing Gaze (#636) becomes a viable option.
This PR not only massively increases our test coverage for the
watcher but also address a bunch of known edge cases i.e. orphaned
imports when a files is deleted.

Closes #1896
Fixes #1891

Readme: Fix typo in alt text of Slack Badge

Add Electron ABI versions

This adds the respective Electron ABI versions to `getHumanNodeVersion()`
to enable running `node-sass` under Electron where the ABI versions differ from Node's.