don't run git_gutter in a view if it has no window

don't run git_gutter in a view if it has no window: fixes AttributeError: 'NoneType'... when views are activated via the `Goto Anything` palette
Issue #100: Marker for new files
loading show_markers_on_untracked_file is unnecessary
Merge branch 'master' of github.com:brunosabot/GitGutter into bruno
Make ignored icon look better
Added info about untracked/ignored icons setting.
Add recommendation for sublime-monokai-extended color scheme.
Start a list of color schemes that define colors for git gutter
Update README.md
Update git_gutter_handler.py

added import encodings
Get back on track with PEP8
bugfix: GitGutter icons can now display in submodules
fix pep8 issue, also added the missing parenthesis
Add Tomorrow Theme to color scheme list
Merge pull request #117 from bbrks/patch-1

Add Tomorrow Theme to color scheme list
Merge branch 'bugfix-submodule-gutter-issue' of github.com:ShengYun/GitGutter into submodule
Merge branch 'master' into custom