Bugfix #1951: text selection in insert mode

[DanEEStar]

Use the normal selection in insert mode.
This fixes #1951. Selection in insert mode seems to be
specific to this plugin and is not easily possible in normal Vim.

[xconverge]

Did you compile with gulp? It should run prettier on your code to fix up whitespace and conform...

[DanEEStar]

I did run with gulp compile.

It did not change any files on my machine. Do you have an idea what I did wrong?

[DanEEStar]

I did run the command from the travis-ci manually:

git ls-tree -r HEAD --name-only | grep ".*.[t|j]s$" | xargs ./node_modules/prettier/bin/prettier.js --write --print-width 100 --single-quote --trailing-comma es5

This did fix some whitespace issues. See next commit.
But it did not fixup my files when running gulp compile before...

[xconverge]

This looks like a nice change and we do less wonky stuff with selection! Thanks!