rst adjustment, hopefully looks like a 'sidebar'

README.rst

@@ -44,12 +44,12 @@ stack, and allows the scheduler to run in main and never be
 evacuated.  [We may eventually generalize this and use several coro
 stacks rather than just one].
 
- [The original version of coro used the unix ucontext API, which on
+ The original version of coro used the unix ucontext API, which on
  FreeBSD 4.X was implemented using very similar assembly.  However,
  FreeBSD 5.X+ moved the ucontext API into the kernel, making it much
  more expensive.  Currently, the 'swap' implementation is about 15
  lines of x86 (or x86_64) assembly.  It saves and restores the stack,
-  frame, and insn pointers in/out of the coro structure.]
+ frame, and insn pointers in/out of the coro structure.
 
 Scheduler
 =========