Logdna

Fix
* **opts:** Repair logging options for each call ([`e326e4c`](https://github.com/logdna/python/commit/e326e4c2461b808b5d3a885b37555f8e610615e4))

Feature
* **meta:** Enable adding custom meta fields ([`f250237`](https://github.com/logdna/python/commit/f250237dbde932e99ab199023516f66a248c5e80))
* **threadWorkerPools:** Introduce extra threads ([`9bfe479`](https://github.com/logdna/python/commit/9bfe479132acb0aa8e5784f2aa31298606e49789))

Documentation
* Update the README as requested ([`5dd754f`](https://github.com/logdna/python/commit/5dd754f177675eb25cd5d5449bd3bcc8286f8739))