Add Descriptive Deprecations

[jeremylow]

Description

Adds a couple things:

• PythonTwitterDeprecation warnings have been added to twitter/error.py. This is in the same vein as Django's warning release system where a deprecation warning is added prior to a release and has the release number included in the warning. So, for example, in version 3.2, there are a bunch of PythonTwitterDeprecation330 warnings letting you know what's going away in the next version.
• In that spirit, the previous deprecation warnings have been converted to PythonTwitterDeprecation330 warnings where appropriate.
• UpdateBackgroundImage now has a PythonTwitterDeprecation330 deprecation warning.

Related Issue

#341

How Has This Been Tested?

Unit tests added for deprecation of UpdateBackgroundImage. All new and old tests pass.

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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This change is

[codecov-io]

Current coverage is 74.27% (diff: 100%)

Merging #386 into master will increase coverage by 0.60%

@@             master       #386   diff @@
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  Files             8          8          
  Lines          1964       1971     +7   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
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+ Hits           1447       1464    +17   
+ Misses          517        507    -10   
  Partials          0          0          

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[bear]

Reviewed 5 of 5 files at r1.
Review status: all files reviewed at latest revision, all discussions resolved.

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