CI: try to add docker build into travis

[zhang-alvin]

Mandatory Checklist

Please ensure that the following criteria are met:

• [ ] Title of pull request describes the changes/features
• [ ] Request at least 2 reviewers
• [ ] If new files are being added, the files are no larger than 100kB. Post the file sizes.
• [ ] Code coverage did not decrease. If this is a bug fix, a test should cover that bug fix. If a new feature is added, a test should be made to cover that feature.
• [ ] New features have appropriate documentation strings (readable by sphinx)
• [ ] Contributor has read and agreed with CONTRIBUTING.md and has added themselves to CONTRIBUTORS.md

As a general rule of thumb, try to follow PEP8 guidelines.

Description

Try to build and then push Docker image to DockerHub for both Dockerfile and Dockerfile.conda

[codecov[bot]]

Codecov Report

Merging #1138 into master will increase coverage by 0.07%. The diff coverage is 92.00%.

@@            Coverage Diff             @@
##           master    #1138      +/-   ##
==========================================
+ Coverage   51.63%   51.70%   +0.07%     
==========================================
  Files         539      540       +1     
  Lines      102272   102376     +104     
==========================================
+ Hits        52805    52935     +130     
+ Misses      49467    49441      -26     

Impacted Files	Coverage Δ
proteus/config/copper.py	0.00% <ø> (ø)
proteus/mprans/RANS3PSed.py	0.00% <0.00%> (ø)
proteus/mprans/VOS3P.py	0.00% <0.00%> (ø)
proteus/tests/TwoPhaseFlow/damBreak_PUMI.py	92.59% <92.59%> (ø)
proteus/MeshAdaptPUMI/AdaptHelper.py	83.29% <100.00%> (+1.87%)	:arrow_up:
proteus/mprans/RANS3PF.py	84.32% <100.00%> (+0.01%)	:arrow_up:
proteus/tests/TwoPhaseFlow/test_TwoPhaseFlow.py	85.48% <100.00%> (+3.48%)	:arrow_up:
proteus/tests/test_boundaryconditions.py	97.20% <0.00%> (-0.13%)	:arrow_down:
proteus/mprans/CLSVOF.py	77.59% <0.00%> (+0.15%)	:arrow_up:
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update a69fe28...24b1359. Read the comment docs.

[zhang-alvin]

Reformatting of function signatures thanks to @JohanMabille has made compilation times a lot faster with less memory usage, enabling dockerhub to build images as desired.

No longer a need for a Travis-based build of the image.