New installation script for UNIX

[ghost]

Hi, Ned here.
In this script, all the logic I used was production-ready and in active use. I guess there shouldn't be any problem with this one.

However, I still ask if you have a working UNIX (eg. macOS or Linux Distros) test this out. Any feedback is appreciated.

Features

• Menu - Tiny & clean prompts to help new users customize their installation.
• Git clone - Manually git clone the repo to provide support for older git versions.
• Config - Automatically generate the config based on the user choices.
• Colored logs - Provide an more easier on the eyes installation proccess with colorful log messages.
• One liner usage - Give the possibility to install dein.vim with just one line for UNIX's users.
• Tiny - The script size is less than 7.5K.

Examples

Test the new script by running one of the following commands:

# curl
sh -c "$(curl -fsSL https://raw.githubusercontent.com/santosned/dein.vim/master/bin/installer.sh)"
# or wget
sh -c "$(wget https://raw.githubusercontent.com/santosned/dein.vim/master/bin/installer.sh -O -)"

In some case users might wan't to keep the current vim config, so to handle that I added the --keep-config | -K arguments, which can be passed to the installation script, like this:

# curl
sh -c "$(curl -fsSL https://raw.githubusercontent.com/santosned/dein.vim/master/bin/installer.sh)" "" --keep-config

When needed this will allow the script to verify if the vim or nvim config exist, if true it'll generate the .vimrc config at the dein.vim base path, if false it'll overwrite any config if existent.

Issues

Closes #467

[Shougo]

I have reviewed.

[ghost]

More than the changes requested, I took the time to clean every other mistake I found.

Now, it's good to go. 🎉

[Shougo]

Hm.. I don't like the default behavior is overwritten.
It breaks older behavior. It does not overwrite.

I think the overwrite is only if users want.

When needed this will allow the script to verify if the vim or nvim config exist, if true it'll generate the .vimrc config at the dein.vim base path, if false it'll overwrite any config if existent.

[Shougo]

keep_config behavior must be default.

[Shougo]

Please take dein installation directory argument for the compatibility.

[Shougo]

Please take dein installation directory argument for the compatibility.

Others are OK.

[Shougo]

Please take dein installation directory argument for the compatibility.

[Shougo]

And please fix README.md.

[ghost]

And please fix README.md.

I could do that. But in another PR, to keep everything clean and organized.

[Shougo]

OK. LGTM.

[Shougo]

Merged. Thanks.