abyss: Fails with clang

error: implicit instantiation of undefined template
'std::__1::hash<cstring>'
abyss: Add 512 to the --enable-maxk options
abyss 1.3.7

No longer fails with clang
seqtk: Add tabtk to head

Install README.md in doc
bedtools 2.18.0
bedtools 2.18.1

No longer fails to build with clang.
octave: keep info manual

Closes #556.
Fix homepage for snid.

Fixes #554.
VTK6: Added C++11 mode support with several optional dependencies.
ITK: Added C++11 mode support with several optional dependencies.
OpenCV: version bump, added C++11 option, added extra SIMD support