Issue 369 reestructure spidermon contrib monitors

[kennyaires]

• Split spidermon/contrib/scrapy/monitors.py's content into different submodules
• Create a spidermon/contrib/scrapy/monitors/ folder
• Create an init.py file inside that folder that imports everything from the submodules for backward compatibility
• Create submodules inside spidermon/contrib/scrapy/monitors/
• Update the docs sections so they import everything from the submodules instead of specifying individual classes out of spidermon/contrib/scrapy/monitors.py

[codecov[bot]]

Codecov Report

Base: 75.93% // Head: 76.00% // Increases project coverage by +0.06% :tada:

Coverage data is based on head (71af654) compared to base (7766fad). Patch coverage: 94.11% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #386 +/- ## ========================================== + Coverage 75.93% 76.00% +0.06% ========================================== Files 73 76 +3 Lines 3179 3188 +9 Branches 376 376 ========================================== + Hits 2414 2423 +9 Misses 695 695 Partials 70 70 ``` | [Impacted Files](https://codecov.io/gh/scrapinghub/spidermon/pull/386?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub) | Coverage Δ | | |---|---|---| | [spidermon/contrib/scrapy/monitors/base.py](https://codecov.io/gh/scrapinghub/spidermon/pull/386?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub#diff-c3BpZGVybW9uL2NvbnRyaWIvc2NyYXB5L21vbml0b3JzL2Jhc2UucHk=) | `92.30% <92.30%> (ø)` | | | [spidermon/contrib/scrapy/monitors/\_\_init\_\_.py](https://codecov.io/gh/scrapinghub/spidermon/pull/386?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub#diff-c3BpZGVybW9uL2NvbnRyaWIvc2NyYXB5L21vbml0b3JzL19faW5pdF9fLnB5) | `100.00% <100.00%> (ø)` | | | [spidermon/contrib/scrapy/monitors/monitors.py](https://codecov.io/gh/scrapinghub/spidermon/pull/386?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub#diff-c3BpZGVybW9uL2NvbnRyaWIvc2NyYXB5L21vbml0b3JzL21vbml0b3JzLnB5) | `97.84% <100.00%> (ø)` | | | [spidermon/contrib/scrapy/monitors/suites.py](https://codecov.io/gh/scrapinghub/spidermon/pull/386?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub#diff-c3BpZGVybW9uL2NvbnRyaWIvc2NyYXB5L21vbml0b3JzL3N1aXRlcy5weQ==) | `100.00% <100.00%> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scrapinghub)

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[kennyaires]

Hi guys,

I made the changes accordingly, please review.

[kennyaires]

Synced with master, ready to merge.

[kennyaires]

synced with master

[VMRuiz]

I tested it locally and it seems to work fine with both old and new paths. Merging it now.