use work buffer settings in v3 engine

create work channel with engine buffer setting (#97)

* create work channel with engine buffer setting

* add test to verify channel buffering behavior

* fmt

v1.2.0 Add more metrics

metrics improvements (#94)

* add metric for watchers

* add prefix to method for crawler get calls

* fmt

* simplify

* refactor for backwards compatibility

* remove method for baseReadAPI

add configurable lock timeout

Add configurable lock timeout (#93)

* Add configurable lock timeout

* Change magic number to other random guess

v1.1.6: Switch to golangci-lint, add gosec (#92)

* Switch to golangci-lint

* Use docker to run etcd (in Travis and locally)

v1.1.5 Add the stack to panic log message

Add stack to panic log (#90)

Migrate to Go Mod (#85)

* Migrate to Go Mod

* Fix tests

* Remove more glide

Update semver constraint for zap

Update the semver constraint for go.uber.org/zap to be permissive of newer ETCD versions

Add extendable metrics collector

Introduced metrics collector interface that can be extended to collect and publish metrics.
The following metrics are collected:

How many lock requests succeed and fail

1. Rule evaluation - how often does a rule evaluate to true then evaluates to false further along in the processing
2. How many times a dynamic rule is evaluated. A dynamic rule can be evaluated multiple times if it's a part of a compound rule. Concrete example, say a compound rule is made up of two rules. The crawler first evaluates rule1, when it's true it then evaluates rule2. Further along the list of patterns the crawler picked up it runs across rule2 again and it evaluates to true. It then finds rule1 again to evaluate it. So the two rules, even through they could have just been evaluated once, were evaluated twice in checking the compound rule.
3. The length of time a triggered rule sits in the worker queue before it's callback is called

Upgrade to go 1.11.5 in Travis

additional spelling corrections and refactoring

Remove client config from engine constructors

v1.0.0

Remove unused config (#77)