fix exception when opening empty folder and file open
Update CONTRIBUTING.md

Add section about "Starter Bugs".
Merge branch 'master' of https://github.com/adobe/brackets into Issue-2509
Merge remote-tracking branch 'upstream/master' into WebsiteDeveloper/ProjectManager
Merge remote-tracking branch 'upstream/master' into WebsiteDeveloper/ProjectManager
Updated ProjectManager.js
Changed to use no-focus class
Update strings.js

update new strings
Updated by ALF automation.
Cleaned up the preferences ids
Fixed forgotten id
Added Localisation for the Loading... message
Cleaned up whitespace and indents
Rewrite _adjustFontSize() so it can adjust font size by more than a single pixel at a time
Add in persistence of font size between Brackets sessions
Limit the maximum negative value of fontSizeAdjustment so the fonts don't get too small
Persisted font sizes now load on currentDocumentChange event
Disable Font Size commands when there is no current document
Update UI appropriately when the application first starts and when the current document changes
Small comment change