TST: make sure test passes even if components link isn't present
closes #4309

@jreback i think this might be broken...

```
In [1]: from pandas.io import data as web

In [2]: web
Out[2]: <module 'pandas.io.data' from 'pandas/io/data.pyc'>

In [3]: web.get_components_yahoo('^NDX')
Out[3]:
      exchange   name
@^NDX      N/A  @^NDX

In [4]: web.get_components_yahoo??

In [5]: web.get_components_yahoo('^DJI')
Out[5]:
      exchange               name
AA        NYSE  Alcoa Inc. Common
AXP       NYSE  American Express
BA        NYSE  Boeing Company (T
BAC       NYSE  Bank of America C
CAT       NYSE  Caterpillar, Inc.
CSCO  NasdaqNM  Cisco Systems, In
CVX       NYSE  Chevron Corporati
DD        NYSE  E.I. du Pont de N
DIS       NYSE  Walt Disney Compa
GE        NYSE  General Electric
HD        NYSE  Home Depot, Inc.
HPQ       NYSE  Hewlett-Packard C
IBM       NYSE  International Bus
INTC  NasdaqNM  Intel Corporation
JNJ       NYSE  Johnson & Johnson
JPM       NYSE  JP Morgan Chase &
KO        NYSE  Coca-Cola Company
MCD       NYSE  McDonald's Corpor
MMM       NYSE  3M Company Common
MRK       NYSE  Merck & Company,
MSFT  NasdaqNM  Microsoft Corpora
PFE       NYSE  Pfizer, Inc. Comm
PG        NYSE  Procter & Gamble
T         NYSE          AT&T Inc.
TRV       NYSE  The Travelers Com
UNH       NYSE  UnitedHealth Grou
UTX       NYSE  United Technologi
VZ        NYSE  Verizon Communica
WMT       NYSE  Wal-Mart Stores,
XOM       NYSE  Exxon Mobil Corpo
```
 i don't think `NDX` is a valid symbol anymore for whateve reason
 yep
just comment out the whole test
 if i figure this out i'll submit another pr
 figured it out

http://finance.yahoo.com/q?s=%5ENDX

the link to components doesn't work so that test should be totally removed or test failure
 or what i could do is check for `len(df)>1` and continue the test if it is, because this was valid at some point and i'm guessing might be in the future
 that would work
 is this the last bug for release 0.12? what's going on with the docs stuff?
