tests/coalaTest.py: Add test case for ignore flag
tests/coalaTest.py: Add test case for ignore flag

Adds a temporary file, then immediately ignores it.
Ideally, coala should ignore the file and do nothing.

Closes https://github.com/coala/coala/issues/4886

coala/coala,SanketDG/coala,coala/coala,jayvdb/coala,SanketDG/coala,jayvdb/coala,coala-analyzer/coala,coala/coala,jayvdb/coala,coala-analyzer/coala,coala-analyzer/coala,SanketDG/coala