fasd integration, tweaks and fixes

• New contrib layer fasd which integrates the command line tool fasd on SPC f z (thanks to mijoharas)
• New variable for git layer: git-magit-status-fullscreen to choose wether the magit status buffer should be displayed in fullscreen or not. Default value is nil. See documentation for more info.
• Various improvements to scala layer: ensime tweaks, auto-completion on . (dot), etc... (thanks to chrisbarrett)
• Use MELPA packages for evil-tutor and neotree (which brings cool icons for NeoTree !)
• Fix custom evil text objects and add new ones (* and /) (thanks to ralesi)
• Fix evil-visualstar
• evil-visualstar support for evil-search-highlight-persist (will be available later on MELPA)
• Better resolution of user home location (thanks to mkcode)
• Move SPC b d (delete buffer and file) to SPC f d to be more accurate with Emacs terminology.