Fixed bug where read_csv ignores dtype arg if input is empty.
The `CParser` implementation for `pd.read_csv` ignores argument `dtype` if the input is empty.  This pull request fixes this so that a DataFrame with the expected column types is returned.

``` Python
import pandas as pd                                                                                           
import cStringIO as stringio                                                                                  

data, dtype = 'a,b', 'i'

df = pd.read_csv(stringio.StringIO(data), dtype={'a': dtype})                                                                                                                                                               
assert df.dtypes[0].kind == dtype, "df.types[0].kind = %r, dtype = %r" % (df.dtypes[0].kind, dtype)
```

``
Traceback (most recent call last):
  File "issue_1.py", line 9, in <module>
    assert df.dtypes[0].kind == dtype, "df.types[0].kind = %r, dtype = %r" % (df.dtypes[0].kind, dtype)
AssertionError: df.types[0].kind = 'O', dtype = 'i'

```
```

this is going to fail when you have duplicate column names (although this is a separate issue), I think that you could deal with it when constructing the dtype dict (where the dtype would only be specificed once as its a dict)

e.g.

`"one,one"`
 add this issue (the pr number) right in-line with the #10467 comment in the whatsnew/v0.17.0 (as its quite related)
 I made the changes you requested and added some tests for duplicate column names.  I found that `read_csv` appends a suffix to the duplicate name so I don't think there's a problem (unless I misunderstood you).

Please let me know if there's something else before the PR can be merged (I can't get the build of my branch to go green right now due to HTTP 404 errors, which are unlikely to do with my changes).
 try setting `mangle_dupe_columns=False` and (in another test) use `names=['one','one']`
 Build is green @jreback - please let me know if there's something I've missed.
 looks good. typo, then pls squash.
 Good catch!  Apologies; should be okay now.

Ps. Did you want me to squash just the typo or all commits?
 to a single commit.thxs
 Done...
 ok lgtm. ping when green.
 @jreback - green! :-)
 green on this page here. (somethimes takes a while)
 @jreback - definitely green now.
 thanks!
