Summary:
Move lib/Fuzzer docs from a README.txt to a proper .rst file.
This change does not add any content, just formatting.
Test Plan: n/a
Reviewers: samsonov
Reviewed By: samsonov
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D8710
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233638 91177308-0d34-0410-b5e6-96231b3b80d8
