ENH: Quoting support in np.genfromtxt(...)

Based off patch in #2211. Implements custom split method and adds new keyword argument ``quoter=`` to ``np.genfromtxt``. The quoting feature also supports escaping.

#### Example usage:
data.txt:
```
"King","Henry, VI"
"Queen","Victoria"
Sir,Isaac Newton
```
Python:
```
>>> np.genfromtxt("data.txt", quoter='"', delimiter=",", dtype="|S20")
array([[b'King', b'Henry, VI'],
       [b'Queen', b'Victoria'],
       [b'Sir', b'Isaac Newton']], 
      dtype='|S20')
```

#### Changes from original patch:
* **Python 3 compatibility**:
   old code was iterating through bytes and not expecting int
* **Bugfix**:
   old code was dropping final word in split implemention
* **Test**:
   added a unit test