Filter based on lambda or some function
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
dataset[dataset.Column1 =="abc123"] # this works fine
dataset.loc[dataset.Column1.startswith("abc")] #this fails
```
#### Problem description

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/2.7/site-packages/pandas/core/generic.py", line 2970, in __getattr__
    return object.__getattribute__(self, name)
AttributeError: 'Series' object has no attribute 'startswith'

Overall intent:
To use a filtering function or a lambda to select a row or reject it.

#### Expected Output
just as == is defined on Series as checking each element, we can also define startswith or other function like re match etc
#### Output of ``pd.show_versions()``

<details>
# Paste the output here pd.show_versions() here
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.10.final.0
python-bits: 64
OS: Darwin
OS-release: 16.6.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.20.1
pytest: None
pip: 9.0.1
setuptools: 18.5
Cython: None
numpy: 1.8.0rc1
scipy: 0.13.0b1
xarray: None
IPython: None
sphinx: None
patsy: None
dateutil: 1.5
pytz: 2013.7
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 1.3.1
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: None
s3fs: None
pandas_gbq: None
pandas_datareader: None
</details>
