Consider removing IE conditionals (/[if IE])

[little-bobby-tables]

Support for conditional comments was removed in IE10, which itself has reached the end of life more than a year ago.

That's not the main reason I'm bringing this up, however. The problem is in the way it's currently implemented in Slime: the content of the conditional is not parsed (like it should be), rather, it is treated as plain text. This defeats the purpose of <!--[if IE]>, which is to inject browser-specific DOM elements.

Fixing the behavior will increase the complexity of the parser — why not just remove it? In case it's absolutely necessary, the conditionals can be inserted as ordinary HTML tags anyway:

<!--[if IE 9]>
    p Get a better browser
<![endif]-->

[Rakoth]

+1 to drop support

[doomspork]

Let's remove it!

[Rakoth]

closed by #128