[bash-completion] Fix custom completion with dynamic loader enabled for non-standard command names (#1564)

Related to #1170.

Fix the solution for commands with non-standard names
where `$cmd` and `$orig_cmd` differ. e.g. `s.foo` -> `s_foo`

Close #1554

Close #1540

Similar to this PR from fzf.vim:
https://github.com/junegunn/fzf.vim/pull/712

Close ##1533

Close #1539

Close #1535

Close #1521

    fzf --color gutter:-1

Close #1529
Close #1468

Fix #1517

Close #1500

Related #1466

Related #1466

This change is not required if you use the install script to generate
~/.fzf.bash or ~/.fzf.zsh which already has the proper guard statement.

Close #1474

fzf will still override LINES and COLUMNS as before but they may not
hold the correct values depending on the default shell.

Close #1314

Close #1482

Close #1485

Close #1423

Fix #1458

* Update .travis.yml and use stages

This updates the .travis.yml configuration to use separate stages for
unittests and CLI tests. The output is now clearer, since for unittests
and CLI tests separate web pages are available.

* Use go modules and simplify build

Close #1455

Only if preview template contains {q}

Fix #1452
Related #1307

Close #867 
Close #1256 

Close #1379

Close #1393