Fix buffer creation and fold remembering, #70 and #56

Use qstrahl's method for non-destructively opening a file. Also, remove
the empty buffer created by :tabnew
Fix winminheight error
Merge pull request #73 from zhaocai/develop

Fix winminheight error: E591: 'winheight' cannot be smaller than 'winminheight': winheight=5
Fix filename handling on windows
Fix window destruction
Merge pull request #74 from Chronial/fix-win-path

Fix filename handling on windows
Merge pull request #76 from Chronial/fix-winclose

Fix window destruction
Merge branch 'dev' into refactor

Conflicts:
	plugin/python/vdebug/ui/vimui/window.py
Merge branch 'dev' into refactor

Conflicts:
	plugin/python/vdebug/ui/vimui/window.py
Split renderers into separate file
Add session class and test