Allow to pass DSN to the Elastica\Client constructor

[renanbr]

Currently I have to handle config options as separated keys in each environment my application is deployed (local, ci, staging, prod...). Things become hard when an environment required an option the other don't...

It could be cool if Elastica\Client's constructor becomes able to parse a single string.

new Elastica\Client('192.168.1.1:9200');

new Elastica\Client('https://user:p4ss@foo.com:9200/elastic;persistent=false;retryOnConflict=2');

[tacman]

Yes, this would be particular helpful on deployments like Heroku, which creates the DSN environment variable when the service is created, but configuring it requires manually breaking it apart into the individual components.

[ruflin]

Do you see a way how we could introduce this without making it a breaking change? In general, +1 on having such a feature.

[alamirault]

PR is now merge, I think @ruflin you can close issue.