Testing framework and travis integration

[fatih]

This is a longstanding issue that I wanted to tackle. After the next release (1.5), I'm thinking to only work on tests. Please comment and add any additional information you think would be useful for us. Here are couple of things that looks interesting:

https://github.com/syngan/vim-vimlint
https://github.com/thinca/vim-themis
https://github.com/junegunn/vader.vim
https://github.com/kana/vim-vspec
https://github.com/janko-m/vim-test

[fatih]

With Vim 8.0 we also have several assert_XXX() functions

[fatih]

We have now initial travis integration with: #1157, which uses the native and new assert_... tests that comes with Vim 8.0