Add query/request timeout support (#589)

* Support query timeout

* Add tests for timeout

* Add browser support for timeout

* Document timeout

Author: pluma

CHANGELOG.md

@@ -15,6 +15,14 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
   implemented in the current ArangoDB 3.4 release candidate. Please note that this API
   is still subject to change and may indeed still change until the 3.4.0 GA release.
 
+### Added
+
+- Added `timeout` option to `db.query` and request methods
+
+  Note that this merely cancels the request. Queries will still be executed
+  and ArangoDB will still continue processing the request, this will merely
+  result in the socket being forcefully disconnected.
+
 ## [6.9.0] - 2018-11-07
 
 ### Changed

docs/Drivers/JS/Reference/Database/Queries.md

@@ -47,6 +47,12 @@ Dirty reads are only available when targeting ArangoDB 3.4 or later,
 see [Compatibility](../../GettingStarted/README.md#compatibility).
 {% endhint %}
 
+Additionally _opts.timeout_ can be set to a non-negative number to force the
+request to be cancelled after that amount of milliseconds. Note that this will
+simply close the connection and not result in the actual query being cancelled
+in ArangoDB, the query will still be executed to completion and continue to
+consume resources in the database or cluster.
+
 If _query_ is an object with _query_ and _bindVars_ properties, those will be
 used as the values of the respective arguments instead.
 
@@ -67,10 +73,9 @@ const cursor = await db.query(aql`
 // -- or --
 
 // Old-school JS with explicit bindVars:
-db.query(
-  "FOR u IN _users FILTER u.authData.active == @active RETURN u.user",
-  { active: true }
-).then(function(cursor) {
+db.query("FOR u IN _users FILTER u.authData.active == @active RETURN u.user", {
+  active: true
+}).then(function(cursor) {
   // cursor is a cursor for the query result
 });
 ```