Make Class Diagrams usable in Stackedit and Live Editor

[monsterkrampe]

This PR resolves all tasks in #748 and therefore also #609.

[coveralls]

Pull Request Test Coverage Report for Build 740

• 27 of 30 (90.0%) changed or added relevant lines in 3 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.04%) to 54.296%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/diagrams/class/classRenderer.js	0	1	0.0%
src/diagrams/class/parser/classDiagram.js	18	20	90.0%

Files with Coverage Reduction	New Missed Lines	%
src/diagrams/class/parser/classDiagram.js	3	56.63%

Totals
Change from base Build 716:	0.04%
Covered Lines:	2056
Relevant Lines:	3759

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💛 - Coveralls

[monsterkrampe]

The issue mentioned by Codeclimate is the following:
It marks export default { ... } statements from different files as duplicates, which does not seem like a real issue to me.

[knsv]

Thx! Would be nice to get further with the class diagrams.

[rafaelbenavent]

Is this supposed to work in StackEdit? It's not working for me.

[monsterkrampe]

@rafaelbenavent it does not work in StackEdit yet (speaking of https://stackedit.io/).
At first mermaid has to release a new Version to npm including this fix.
Then Stackedit has to upgrade the mermaid dependency.

This PR is a prerequisite to make the classDiagrams work in Stackedit, thus the name. I also tried that out locally with the Stackedit repo.

You can try that out too by cloning the Stackedit Repo.
Then you should only need to edit the package.json and change the mermaid dependency:
"mermaid": "knsv/mermaid#master"