now project_dir always will be stored as absolute path in the context.

[igorborgest]

Requested here: #940

Description of changes:
Now project_dir always will be stored as absolute path in the context. This will allow use absolute or relative paths in the --project-dir CLI parameter.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #1037 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #1037      +/-   ##
=========================================
+ Coverage   95.47%   95.5%   +0.02%     
=========================================
  Files          27      27              
  Lines        4488    4490       +2     
  Branches      563     564       +1     
=========================================
+ Hits         4285    4288       +3     
  Misses        131     131              
+ Partials       72      71       -1

Impacted Files	Coverage Δ
chalice/cli/__init__.py	87.87% <100%> (+0.47%)	⬆️

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[igorborgest]

I used the pytest.mark.parametrize feature to improve the code coverage. I think that increases the coverage in a elegant way.