OpenCV: support for --head install.

Closes #848.
Update to version 8.0.20

Closes #847.
Fix x11 dependency.

See Homebrew/homebrew#28096.
Fix x11 dependency guideline.

See Homebrew/homebrew#28096.

Closes #846.
libccd: collision detection between convex shapes

This is used by the dartsim and gazebo robotic simulators for
collision checking.

Closes #811.
consed 27.0: New formula

A Finishing Package (BAM File Viewer, Assembly Editor, Autofinish,
Autoreport, Autoedit, and Align Reads To Reference Sequence)
edirect 1.70
CONTRIBUTING: add Table of Contents, adjust heading style
viennarna 2.1.7
reapr 1.0.17

Fixes #851.
igv: Add DOI and head
bali-phy 2.3.0

Closes #852.
bedops: update sha1
mbsystem 5.4.2183
abyss 1.5.0

Add DOI
trans-abyss: Add DOI
bali-phy 2.3.1

Closes #855.
maker 2.31.3
root: revert to X11 for default backend

Closes #854.
Reverts f1ecc89.
radx 20140417