Updated to WatchmanWatcher, created singleton WatchmanClient using pr…

…omises (#109)

* minor typo fixes

* created singleton WatchmanClient, uses promises. Updated WatchmanWatcher to use it instead of direct connection to watchman.Client. Also made WatchmanClient call know WW APIs, instead of trying to handle with EventEmitter.

* minor typo fix, removed test code to force call to WC.onEnd for testing reconnect

* updated to new code style based on PR feedback from Stef

* further updates based on Stef comments

* created _watcherMap using Object.create()

* fixed up watchman_client to support multiple binary paths, added getInstance(), reworked the client setup mechanism to avoid possible race conditions, cleaned WatchmanWatcher to style standard that Stef Penner mentioned

* moved backoffTimes to a function so we can have one obj per watchmanBinaryPath (i.e. WatchmanClient). Also added try/catch in _handleClientAndCheck in case return value from capabilityCheck is somehow malformed or attaching listeners to watchman.Client does not work

* removed catch from promise chain, so callers will be responsible for the rejected promise (which they should be anyway)

README.md

@@ -34,7 +34,7 @@ maintains the same API across all modes and will be easy to switch.
 
 ### sane(dir, options)
 
-Watches a directory and all it's descendant directories for changes, deletions, and additions on files and directories.
+Watches a directory and all its descendant directories for changes, deletions, and additions on files and directories.
 
 ```js
 var watcher = sane('path/to/dir', {glob: ['**/*.js', '**/*.css']});