Update buffer key bindings documentation and remove lambdas

Add confirmation for revert and erase functions.
Fixes #136 add truncate lines toggle key bindings

Also update the documentation about toggles and simplify the
toggle frame related bindings
Update evil-plugins submodule
Add makefile to launch tests and dummy tests

Using ERT
Add CONVENTIONS.md file
Fixes #146 Add support for fancy-battery in mode-line
Add quick install to readme
Readme modifications (key bindings and contribution)
Typo in readme
Replace lambda for `<SPC> TAB` with spacemacs/last-buffer
Remove unneeded variable spacemacs-mode-line-flycheckp
Remove projectile-commander. Define explicit key bindings

This is better because now `<SPC> p` is a correct prefix binding
and we can benefit from guide-key and `<SPC> ?`
Merge branch 'develop' (v0.16.0)