Navigation tray button does not have discernable text display

[sestrauss]

Hello,

Thank you for this great theme. I ran it through the aXe accessibility checker (https://www.deque.com/products/aXe/) and found a number of issues. One key issue, marked as critical, is that the navigation tray button on the top right does not "have discernible text".

According to aXe:

Issue description

Ensures buttons have discernible text
Impact: critical

Element location
#yui_3_17_2_1_1520625261252_364

Element source
<button aria-expanded="false" aria-controls="nav-drawer" type="button" class="btn pull-xs-left m-r-1 btn-secondary" data-action="toggle-drawer" data-side="left" data-preference="drawer-open-nav" id="yui_3_17_2_1_1520625261252_364">