'debugger-style' API

[ndrewh]

# Run until a pc is reached
p.run_until(0x123456)

# Run until a 'breakpoint' is reached
p.cont()

How this works with hooks is TBD, but I would assume that hooks would execute at all times by default.

Potential use case (pseudocode):

while tcache_is_not_full(p, 0x100):
    p.send("a" * 0x100)
    p.run_until(0x12345678)

[ndrewh]

Following from #17, we need the following restriction:

p.run_until(...) can only be called when:

• The application is stopped (i.e. it cannot have been resumed due to a previous p.recv() call)
• AND the call is in the top-level context for a thread (i.e. the outermost scope of the script, or the outermost
  scope of a thread entry hook). run_until is not valid in hooks*

*i think that nested hooks would cause a problem.

[ndrewh]

opened #26 to ensure the examples from this issue gets made