Removed `lakestrip.6144x2000 copy.png`

• Removed extra unneeded `graphics/lakestrip.6144x2000 copy.png` file.
Bootstrap-media-query resized lakestrips

• `lakestrip.6144x2000.png` downscaled to:
	◦ `lakestrip.1920x625.png`, for devices fitting Bootstrap’s `lg` classes (Desktops ≥1200px wide)
	◦ `lakestrip.1199x390.png`, for Bootstrap’s `md` classes (Desktops 992px-1199px wide)
	◦ `lakestrip.991x323.png`, for Bootstrap’s `sm` classes (Tablets 768px-991px wide)
	◦ `lakestrip.767x250.png`, for Bootstrap’s `xs` classes (Phones ≤767px wide)
	» These variations will allow bigger-screen devices to get a high-quality image, while letting smaller-screen devices which’ll never see that detail download smaller-file-size variants.
• Also: Removed `lakestrip.2000x640.png`, since 1920-wide is being used instead here.
Added #lakestrip back image

• Added a `#lakestrip.back.image` div under the title-phase’s `.back.fill`.
	» Within the back fill instead of after-it-as-a-sibling because… I don’t know, fewer elements?  Maybe I should’ve done the sky-phase’s fill this way too.  I guess this is a test to make sure both approaches work on all browsers.
• New `#lakestrip {}` CSS sets up the lakestrip graphics to be used as the `background-image` for each of Boostraps media query modes (`max-width: @screen-xs-max`, `min-width: @screen-sm`, `min-width: @screen-md`, and `min-width: @screen-lg`).
	• Separate `background-repeat`/`-size`/`-position` properties set it to not repeat, be 100% width with aspect-ratio-auto height, and be position at x=0, y=50%.
Added parallax animation to #lakestrip

• Added a `.-skrollr-dry-animation()` call to parallax-animate #lakestrip’s background-position linearly (for now) from `0 200%` at title_phase_appear to `0 40%` at title_phase_close.
	• Setting the initial CSS background-position to the `@endScrollOffset` since that’s the intended final resting state, so we want it there just-in-case the user doesn’t have JS.