Protect against detached browser.
Merge pull request #249 from adobe/glenn/crash-on-refresh

Fix potential crash when reloading Brackets
On Windows, support launching brackets from the command line with a
parameter of the form "filepath[:lineNumber[:columnNumber]]". This is the
windows implementation of my recent macintosh pull request.
Merge branch 'master' of https://github.com/adobe/brackets-shell into marks/open-line-col