PR: Skip some tests in our CIs

[ccordoba12]

Some tests run fine locally but fail like crazy in our CIs. Others are timing out too much on Windows (and block Appveyor for an hour!).

[skip pep8]

[pep8speaks]

Hello @ccordoba12! Thanks for submitting the PR.

• In the file spyder/app/tests/test_mainwindow.py, following are the PEP8 issues :

Line 136:80: E501 line too long (82 > 79 characters)

• In the file spyder/plugins/tests/test_ipythonconsole.py, following are the PEP8 issues :

Line 85:80: E501 line too long (80 > 79 characters)
Line 106:80: E501 line too long (80 > 79 characters)