README: Clarify handling of passwords/credentials

Fixes #51.
Added Appstr.io install page
Updated Appstr install page
Merge branch 'gh-pages'
Published with http://benweet.github.io/stackedit/
Merge pull request #52 from certik/patch-1

README: Clarify handling of passwords/credentials
Merge branch 'master' of github.com:benweet/stackedit
Published with http://benweet.github.io/stackedit/
Published with http://benweet.github.io/stackedit/
Published with http://benweet.github.io/stackedit/
Merge branch 'master' of github.com:benweet/stackedit
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