Allow users to import CSV data

Allowing users to read in CSV data would come in handy. For instance, Google Chrome store exports statistics into CSV files. Analyzing them in pychart would be nice.

PyChart would ideally read in the CSV file and format to a given chart type.

Example code could be: `chart_instance = PyChart.import_CSV(file="files/path.csv", type="bar")` where file is a path to the specific CSV file and type is a type of chart (bar, scatter, pie, etc).

Example data might resemble:

```
"Date","Impressions","Installations"
"2016-02-08","115.0","3.0"
"2016-02-09","146.0","1.0"
"2016-02-10","152.0","1.0"
"2016-02-11","143.0","0.0"
"2016-02-12","123.0","2.0"
"2016-02-13","111.0","1.0"
"2016-02-14","110.0","1.0"
"2016-02-15","183.0","0.0"
"2016-02-16","185.0","4.0"
"2016-02-17","228.0","1.0"
"2016-02-18","257.0","1.0"
...
```