Add travis step to check whitespace

[ccope]

• [X] Add the code checks, get red build
• [x] Apply fixes, get green build
• [x] Commit .git-blame-ignore-revs file after review

[ccope]

Example of a failing build: https://app.travis-ci.com/github/libfuse/sshfs/builds/236422045

[ccope]

This supersedes the whitespace fixes in #257 but the editorconfig would still be useful.

[Nikratio]

Looks good, thank you!

[Nikratio]

Could you make the .git-blame-ignore-revs as well, now that this is merged?