Allow episode search without episode number

[evuez]

This fixes #692.

Not finding the episode number shouldn't raise an error, most of the time
it actually works without one anyway.

[coveralls]

Coverage remained the same at 91.821% when pulling ff6ae65 on evuez:allow-no-number into 7eb7a53 on Diaoul:develop.

[coveralls]

Coverage remained the same at 91.821% when pulling ff6ae65 on evuez:allow-no-number into 7eb7a53 on Diaoul:develop.

[fernandog]

@evuez I would check episode number OR 'date' as in guessit result:

guessit "Panorama.2016.06.29.Iraq.The.Final.Judgement.720p.WEB-DL.h264-OmarMateen.mkv"
For: Panorama.2016.06.29.Iraq.The.Final.Judgement.720p.WEB-DL.h264-OmarMateen.mkv
GuessIt found: {
    "title": "Panorama",
    "date": "2016-06-29",
    "country": "IRAQ",
    "episode_title": "The Final Judgement",
    "screen_size": "720p",
    "format": "WEB-DL",
    "video_codec": "h264",
    "release_group": "OmarMateen",
    "container": "mkv",
    "mimetype": "video/x-matroska",
    "type": "episode"
}

Because it can't have an episode number and also can't be air by date

[fernandog]

check date from guessit

[fernandog]

@evuez
Also all providers needs to be changed to add a "match" when date is equal in both video and subtitle

[fernandog]

@Diaoul how to proceed with this? as the air-by-date would override season and episode. The score system will need to be changed. And as discussed in our talk, we should consider add edition and streaming_services to the score too. Maybe we can do all this in a new PR

ping @pannal @ratoaq2