Implement block shapes to latest spec

[tmickel]

-Convert most constants in the code to use multiplications of GRID_UNIT (4px). This lets us be consistent with Carl's specs and helps explain the numbers a little better.
-Implement notches using cubic curves instead of arcs. This version matches the spec pretty much exactly. As part of this, remove NOTCH_BASE_HEIGHT which is no longer relevant.
-Slight simplification of renderCompute_ (which calculates metrics).
-Fixed SEP_SPACE_X and SEP_SPACE_Y to be the correct number of grid units. Our blocks before were slightly too small, now they are the right size.
-Implement the correct corner radius, hat/end hat radius.
-Add fixed ICON_WIDTH and ICON_HEIGHT, i.e., always size the icons to 40x40px as according to the spec.
-Add fixed STATEMENT_BLOCK_SPACE to represent the size of the bar above forever/repeat/pants blocks. Previously the code was assuming this was SEP_SPACE_Y, when in fact the spec has it as larger (4 units).
-Add accurate MIN_BLOCK_X and MIN_BLOCK_Y for simpler calculation of minimum bay size.
-Remove some unused SVG paths (INNER_TOP_LEFT_CORNER, INNER_BOTTOM_LEFT_CORNER).
-Remove extra code in getHeightWidth which caused a bug in rendering forever-in-repeat.
-Fix stroke width around the blocks to be 1px, according to spec.

I've checked that everything lines up with Carl's spec images at 8x zoom.

This should implement #69, #70, #71, #72, #74, and #75 (not 73 as we haven't done that input yet).

[thisandagain]

This looks great @tmickel . One minor nitpick but otherwise good to land. How would you feel about squashing these commits?

[rachel-fenichel]

Not finished for RTL

On Tue, Mar 1, 2016 at 12:29 PM Tim Mickel notifications@github.com wrote:

Closed #99 #99.

—
Reply to this email directly or view it on GitHub
#99 (comment).

[tmickel]

True - considering that separately (#34)

[rachel-fenichel]

I don't think we should have extremely granular issues open for visuals and then have a single catchall "implement RTL" issue--I think issues should be left open until they are resolved for both ltr and rtl.