Writer implementation

* Update README with Writer example and changelog
* Fixed nsqdconnection member initialization
* Slight refactor of nsqdconnection / ConnectionState to support writer
* Renamed NSQDConnection's SUBSCRIBED event to READY so that it makes
sense in both the Reader and Writer cases.
* Added NSQDConnectionWriter
* Additional check for Reader options parameters
* Added `lookupd.coffee` to refactor the logic for querying lookupds
for nodes.
* Updated `Reader` to use the `lookupd` module functionality.
README fixes

* Example description for Writer was wrong
* Described the `publish` method on Writer objects.
Writer now doesn't use lookupd

* Updated README to remove Writer options and use just host / port pair
* Refactoring of NSQDConnection and ConnectionState to remove hideous
`isReady` parameter
* Writer now just allows directly connecting to an nsqd. No more
discovery via lookupd.
* Added nock dependency
* Added tests for lookupd module
Missing `request` in package.json
More lookupd module tests, lookupd module refactor

* Refactored tests for lookupd module
* Added tests for lookupd.lookup
* Refactored shared logic between `nodes` and `lookup` in `lookupd`
module
Removed unused error message
Removed `nodes` from lookupd module since it's unused

* Removed tests for `nodes`
* Removed `nodes` from `lookupd`
* `lookup` function is now exported as the default from `lookupd` module
Errors vs asserts and other style issues

* Replace asserts with Errors
* Style issues
Two more style issues
Merge master
Merge pull request #8 from dudleycarr/writer

Writer implementation