v0.7 wip

* [x] rename the term context into solution, as it's more clear #31.
* [x] move from " to '.
* [x] rename `join()` to `search()`.
* [x] introduce filtering #27 in `search()` and `get()`
* [x] introduce a `'limit'` and `'offset'` option in `search()` and `get()`.
* [x] callback to avoid deferred open #46.
* [x] saucelabs testing

Closes #45.