Panel resample fails for degenerate panels
#### Code Sample, a copy-pastable example if possible

```
import numpy as np
import pandas as pd

dr = pd.date_range('20100101','20151231',freq='T')
p1 = pd.Panel(items = dr, data=np.random.randn(len(dr),3,3))
#this works
p2 = p1.resample('D', axis=0, how='last')
p3 = pd.Panel(items = dr, data=np.random.randn(len(dr),1,1))
#this causes an error
p4 = p3.resample('D', axis=0, how='last')
```
#### Expected Output
#### output of `pd.show_versions()`
## INSTALLED VERSIONS

commit: None
python: 3.5.1.final.0
python-bits: 64
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 58 Stepping 9, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None

pandas: 0.17.1
nose: 1.3.7
pip: 8.0.2
setuptools: 19.6.2
Cython: 0.23.4
numpy: 1.10.4
scipy: 0.17.0
statsmodels: 0.6.1
IPython: None
sphinx: 1.3.1
patsy: 0.4.0
dateutil: 2.4.2
pytz: 2015.7
blosc: None
bottleneck: 1.0.0
tables: 3.2.2
numexpr: 2.4.6
matplotlib: 1.5.1
openpyxl: 2.3.2
xlrd: 0.9.4
xlwt: 1.0.0
xlsxwriter: 0.8.4
lxml: 3.5.0
bs4: 4.4.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.11
pymysql: None
psycopg2: None
Jinja2: 2.8
