Add various useful commands

* Shell command opens split with results from running command
* * Similar to !<command>
* Find merge conflict search
* Tag files can be placed in .git/tags and will be found at all levels
  of a git repository
* New airline separators
* Allow repeating visual mode commands
* Minor formatting
Merge pull request #429 from sbennett18/3.0

Add various useful commands
Add mappings for some more fugitive commands: Gread and Gedit
Workaround fix for vim-gitgutter issue #106

Reference
https://github.com/airblade/vim-gitgutter/issues/106
Merge pull request #433 from beepscore/3.0

Workaround fix for vim-gitgutter issue #106
Source optional .vimrc.before

Adding an optional .vimrc.before as suggested by @spf13 in Issue #428
Merge pull request #432 from jcromero/3.0

Add mappings for some more fugitive commands: Gread and Gedit
Merge pull request #434 from mikedfunk/patch-1

Source optional .vimrc.before
Merge remote-tracking branch 'spf13/3.0' into 3.0
Merge remote-tracking branch 'origin/3.0'