Column name 'class' causes access and query issues
For some reason pandas isn't liking when I create a column named class and attempt to access with .{columnname} method

I also cannot run a query on the dataframe. 

Code:

``` python
>>> a = pandas.DataFrame({'class':[0], 'clas1': [1]})
>>> a.clas1
0    1
Name: clas1, dtype: int64
>>> a.class
  File "<stdin>", line 1
    a.class
          ^
SyntaxError: invalid syntax
>>> a.query("clas1==1")
   clas1  class
0      1      0
>>> a.query("class==0")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.4/site-packages/pandas/core/frame.py", line 1918, in query
    res = self.eval(expr, **kwargs)
  File "/usr/lib/python3.4/site-packages/pandas/core/frame.py", line 1970, in eval
    return _eval(expr, **kwargs)
  File "/usr/lib/python3.4/site-packages/pandas/computation/eval.py", line 230, in eval
    truediv=truediv)
  File "/usr/lib/python3.4/site-packages/pandas/computation/expr.py", line 635, in __init__
    self.terms = self.parse()
  File "/usr/lib/python3.4/site-packages/pandas/computation/expr.py", line 652, in parse
    return self._visitor.visit(self.expr)
  File "/usr/lib/python3.4/site-packages/pandas/computation/expr.py", line 310, in visit
    node = ast.fix_missing_locations(ast.parse(clean))
  File "/usr/lib/python3.4/ast.py", line 35, in parse
    return compile(source, filename, mode, PyCF_ONLY_AST)
  File "<unknown>", line 1
    class ==0 
           ^
SyntaxError: invalid syntax

```

Dependencies: 
## INSTALLED VERSIONS

commit: None
python: 3.4.3.final.0
python-bits: 64
OS: Linux
OS-release: 3.18.6-1-ARCH
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: en_US.utf8

pandas: 0.15.2
nose: 1.3.4
Cython: None
numpy: 1.9.2
scipy: 0.15.1
statsmodels: None
IPython: 3.0.0
sphinx: None
patsy: None
dateutil: 2.4.1
pytz: 2014.10
bottleneck: 1.0.0
tables: 3.1.1
numexpr: 2.4
matplotlib: 1.4.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
rpy2: None
sqlalchemy: None
pymysql: None
psycopg2: None
