Sync with distributed 2.0 and dask 2.0

[andersy005]

• Drops Python 2
• Fixes broken APIs
• Fixes Drop Python 2.7 tests? #34
• Fixes uri_from_host_port moved #35

@kmpaul,

I wasn't sure of what to do when parsing the environment.yml when versions are specified with >= or <=. So, I commented these two lines out in def environment_dependencies function in setup.py for the time being:

if isinstance(obj, string_types):	
        dependencies.append(obj.replace('=', '=='))

[codecov]

Codecov Report

Merging #36 into master will decrease coverage by 0.14%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #36      +/-   ##
==========================================
- Coverage   93.93%   93.79%   -0.15%     
==========================================
  Files           4        4              
  Lines         132      129       -3     
==========================================
- Hits          124      121       -3     
  Misses          8        8

Impacted Files	Coverage Δ
dask_mpi/cli.py	96.96% <ø> (-0.09%)	⬇️
dask_mpi/core.py	100% <ø> (ø)	⬆️
dask_mpi/common.py	87.71% <100%> (-0.22%)	⬇️

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[mrocklin]

I would expect both distributed and click to come by default in the dask metapackage.

[mrocklin]

This seems good to me. Thanks @andersy005 !

[kmpaul]

Nice job, @andersy005! This looks good.