Calling `obspy.taup.taup.getTravelTimes` repeatedly eventually fails.

As in the following example,

```
In [1]: from obspy.taup.taup import getTravelTimes

In [2]: len(getTravelTimes(delta=22, depth=0, model='ak135'))
Out[2]: 21

In [3]: for i in xrange(0,180,2):
    for d in xrange(0, 700, 5):
        x = getTravelTimes(delta=i, depth=d, model='ak135')
   ...:         
python: More than 60 arrivals found.                                       : Success
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain
python: More than 60 arrivals found.                                       : Numerical argument out of domain

In [4]: len(getTravelTimes(delta=22, depth=0, model='ak135'))
python: More than 60 arrivals found.                                       : Success
Out[4]: 57
```

In the first call, 21 arrivals are found, but after calling `getTravelTimes` several times (perhaps a bit more than necessary to trigger the bug), "More than 60 arrivals" are found.