---- Summary ----

A text inside the issue form's textarea and the submit button should now
be gray when the element is disabled. Any other style changes are
unintentional and can be considered as bugs (if it looks worse then
before).

Despite some breaks are possible, my thought is that going forward with
actual normalize.css is good choice and any bugs will visible and
therefore will be fixed sooner or latter.

---- Details ----

The original intention was to get fix for color of disabled form's
elements from [1]. It removes `color: inherit` from rules for forms
elements, which affected enabled and disabled elements both. The
intention was to fix the issue form when some elements are disabled.

During testing of the new normalize.css I found that textarea is colored
black despite other text has some other default color (#2e3436). It's
maybe due to my browser has non-so-standard configuration (Firefox 47.0
with dark devedition theme enabled), but anyway it's possible user's
configuration. I added back `color: inherit` for issue form rules and
add `color: graytext` for disabled elements.

New normalize.css also replaces `font: inherit` for form elements with
choosen default (sans-serif, 100%, 1.15 line-height), see [2]. It
doesn't work well when the default font was replaced with some other.
So I added this rule back for the issue form.

There is one more found difference. Search form at the top of the page
cut from right side with the new normalize.css. It's due to reverting
the box-sizing rule, see [3]. I added back `box-sizing: content-box` to
the rules for search input element.

[1]: necolas/normalize.css#502
[2]: necolas/normalize.css#607
[3]: necolas/normalize.css#496