RFC: Deprecate or fix old/broken DefaultDict constructors

[kmsquire]

• Dict and OrderedDict constructors have changed, and
  DefaultDict/DefaultOrderedDict haven't kept up.

• The changes:

  Dict(KeyType, ValType) => Dict{KeyType, ValType}()
  Dict(ks, vs) is deprectated

• This deprecates working versions of these from DefaultDict
  and friends, and fixes broken calls which attempt to
  use these old constructors.

[codecov-io]

Current coverage is 92.92% (diff: 100%)

Merging #233 into master will increase coverage by 0.70%

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  Files            29         29          
  Lines          2351       2346     -5   
  Methods           0          0          
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+ Hits           2168       2180    +12   
+ Misses          183        166    -17   
  Partials          0          0          

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[kmsquire]

This PR should be ready for review. Linux builds all passed, osx builds are still waiting to run. (We need to enable AppVeyor at some point... @tkelman, might you help with that?)

The functional changes shouldn't be controversial (just updating the interfaces), but a quick review would still be welcome.
For the deprecated functions, I arbitrarily assigned a Julia version in which to remove the deprecations. Any thoughts (👍 or 👎 ) would be welcome.

cc: @DanielArndt @rawls238

[kmsquire]

Everything passes. Will merge tomorrow if there are no comments.

[tkelman]

should mostly just be adding a yml file to enable appveyor, though may need to manually set the webhook if something goes wrong with enabling the repo from the appveyor ui.

[rawls238]

LGTM

[kmsquire]

Thanks @rawls238