Rewrite Ubuntu install instructions.  Skip sketchy install scripts.
Rewrite Ubuntu install instructions.  Skip sketchy install scripts.

No need for pip; Ubuntu 14.04 has everything we need.  Explain
virtualenv option.  Users who want to inflict pip on their systems
can figure out how to do that themselves.

mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,probcomp/crosscat,probcomp/crosscat,fivejjs/crosscat,probcomp/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,mit-probabilistic-computing-project/crosscat,mit-probabilistic-computing-project/crosscat,fivejjs/crosscat,fivejjs/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat,probcomp/crosscat