Reader / Writer context manager

[kaykay-dv]

Python Context Manager classes should be added for reading / writing from indices. Closing connections should be automatically handled by the context managers:

e.g.

from pocketsearch import PocketWriter

with PocketWriter() as pocket_writer
    pocket_writer.insert(text="Hello world.")
    self.assertEqual(pocketsearch.search().count(),1)

and

from pocketsearch import PocketReader

with PocketReader() as pocket_reader:
    self.assertEqual(pocket_reader.search(text="Hello world.").count(),0)

[kaykay-dv]

Implemented in 0.12