Increasing minimum cython version silently breaks build_ext --inplace
#### Code Sample, a copy-pastable example if possible

```
pietro@ecomp:~/nobackup/repo/pandas_test$ python3 setup.py build_ext --inplace
running build_ext
```

```python
In [1]: import pandas as pd
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
/home/pietro/nobackup/repo/pandas_test/pandas/__init__.py in <module>()
     25 try:
---> 26     from pandas._libs import (hashtable as _hashtable,
     27                              lib as _lib,

/home/pietro/nobackup/repo/pandas_test/pandas/_libs/__init__.py in <module>()
      3
----> 4 from .tslib import iNaT, NaT, Timestamp, Timedelta, OutOfBoundsDatetime
      5

/home/pietro/nobackup/repo/pandas_test/pandas/_libs/tslibs/conversion.pxd in init pandas._libs.tslib (pandas/_libs/tslib.c:19007)()
     10
---> 11 cdef class _TSObject:
     12     cdef:

/home/pietro/nobackup/repo/pandas_test/pandas/_libs/tslibs/__init__.py in <module>()
      3
----> 4 from .conversion import normalize_date, localize_pydatetime, tz_convert_single
      5 from .nattype import NaT, iNaT

ImportError: cannot import name 'normalize_date'

During handling of the above exception, another exception occurred:

ImportError                               Traceback (most recent call last)
<ipython-input-1-af55e7023913> in <module>()
----> 1 import pandas as pd

/home/pietro/nobackup/repo/pandas_test/pandas/__init__.py in <module>()
     33                       "pandas from the source directory, you may need to run "
     34                       "'python setup.py build_ext --inplace --force' to build "
---> 35                       "the C extensions first.".format(module))
     36
     37 from datetime import datetime

ImportError: C extension: 'normalize_date' not built. If you want to import pandas from the source directory, you may need to run 'python setup.py build_ext --inplace --force' to build the C extensions first.
```

#### Problem description

When the minimum required Cython version is increased (above the installed one), _but_ there is a version of the compiled code available, ``python setup.py build_ext --inplace`` silently skips compilation.

It should be at least emit a warning that the available Cython version is too old.

#### Expected Output

A warning when running ``python setup.py build_ext --inplace``.

The above is "fixed" if I remove the check for the ``cython >= '0.28.2'``.

#### Output of ``pd.show_versions()``

(after disabling the check for the minimum Cython version, and re-running ``python setup.py build_ext --inplace`` )

<details>

INSTALLED VERSIONS
------------------
commit: 5cb5880d8f1647e303ba52487dc867db838fd6e0
python: 3.5.3.final.0
python-bits: 64
OS: Linux
OS-release: 4.9.0-6-amd64
machine: x86_64
processor:
byteorder: little
LC_ALL: None
LANG: en_GB.UTF-8
LOCALE: en_GB.UTF-8

pandas: 0.24.0.dev0+269.g5cb5880d8.dirty
pytest: 3.0.6
pip: 9.0.1
setuptools: 33.1.1
Cython: 0.25.2
numpy: 1.12.1
scipy: 0.18.1
pyarrow: None
xarray: None
IPython: 5.2.2
sphinx: None
patsy: 0.4.1+dev
dateutil: 2.6.0
pytz: 2016.10
blosc: None
bottleneck: 1.2.0
tables: 3.3.0
numexpr: 2.6.1
feather: 0.3.1
matplotlib: 2.0.0
openpyxl: 2.3.0
xlrd: 1.0.0
xlwt: 1.2.0
xlsxwriter: None
lxml: 3.7.1
bs4: 4.5.3
html5lib: 0.999999999
sqlalchemy: 1.0.15
pymysql: None
psycopg2: None
jinja2: 2.8
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
gcsfs: None


</details>
