specific-column-is-last 
#### Code Sample, a copy-pastable example if possible

 df.columns
 Index([u'a', u'b', u'c', u'd'], dtype='object')

Dont do this, looks like a bug.

 df.columns.drop(["b"]).insert(-1, 'b')
 Index([u'a', u'c', u'b', u'd'], dtype='object')

 df.columns.drop(["b"]).insert(-1, 'x')
 Index([u'a', u'c', u'x', u'd'], dtype='object')
WORK Around:

 df.columns.drop(["b"]).insert(99999, 'b')
 Index([u'a', u'c', u'd', u'b'], dtype='object')
#### Expected Output

 df.columns.drop(["b"]).insert(-1, 'b')
 Index([u'a', u'c', u'd', u'b'], dtype='object')
#### output of `pd.show_versions()`

pandas 18.1

http://stackoverflow.com/questions/38601841/what-is-the-quickest-way-to-ensure-a-specific-column-is-last-or-first-in-a-dat/38602601#38602601
## INSTALLED VERSIONS

commit: None
python: 2.7.9.final.0
python-bits: 64
OS: Linux
OS-release: 4.1.12-1-default
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.utf8

pandas: 0.18.1
nose: 1.3.7
pip: 8.1.2
setuptools: 24.0.2
Cython: None
numpy: 1.11.1
scipy: 0.17.0
statsmodels: None
xarray: None
IPython: 4.1.1
sphinx: 1.4.4
patsy: 0.4.0
dateutil: 2.5.3
pytz: 2016.4
blosc: 1.2.8
bottleneck: None
tables: None
numexpr: 2.4.6
matplotlib: 1.5.1
openpyxl: None
xlrd: 0.9.4
xlwt: 1.0.0
xlsxwriter: 0.8.4
lxml: 3.2.3
bs4: 4.3.2
html5lib: 0.9999999
httplib2: 0.9.1
apiclient: 1.4.2
sqlalchemy: 1.0.11
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.38.0
pandas_datareader: 0.2.1
