Add ecephys optotagging tutorial

[jsiegle]

Add new ecephys notebook, and add link to docs page

[review-notebook-app]

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[jsiegle]

I rebased to rc/1.5.0, but it looks like Travis build is still failing...did I do something wrong?

[kschelonka]

Closing and reopening to trigger build on new target branch.

[codecov-io]

Codecov Report

Merging #1375 into rc/1.6.0 will increase coverage by 0.09%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##           rc/1.6.0    #1375      +/-   ##
============================================
+ Coverage     34.55%   34.64%   +0.09%     
============================================
  Files           342      342              
  Lines         33250    33552     +302     
============================================
+ Hits          11488    11625     +137     
- Misses        21762    21927     +165

Impacted Files	Coverage Δ
allensdk/internal/api/behavior_data_lims_api.py	53% <0%> (-1.38%)	⬇️
allensdk/core/authentication.py	97.67% <0%> (+2.32%)	⬆️
allensdk/brain_observatory/sync_dataset.py	27.73% <0%> (+4.8%)	⬆️
...lensdk/brain_observatory/behavior/sync/__init__.py	44.44% <0%> (+18.58%)	⬆️

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[kschelonka]

Hi @jsiegle, sorry about the build issues. Your rebase was correct -- the issue was on forks not being able to access Travis variables we'd set.