Check validity of Preferences.sublime-settings before modifying.
Check validity of Preferences.sublime-settings before modifying.

Closes #131

smanolloff/SublimeLinter3,jasonrhaas/SublimeLinter3,ikappas/SublimeLinter3,smanolloff/SublimeLinter3,zenlambda/SublimeLinter3,Raynos/SublimeLinter3-raynos,ikappas/SublimeLinter3,jasonrhaas/SublimeLinter3,SublimeLinter/SublimeLinter3,zenlambda/SublimeLinter3,SublimeLinter/SublimeLinter3,paulirish/SublimeLinter3,simonzack/SublimeLinter3,simonzack/SublimeLinter3,paulirish/SublimeLinter3