Create to_elastic method
### Code Sample, a copy-pastable example if possible


### Problem description

Create method to export a pandas dataframe data to elasticsearch json format like to_excel, to_csv, to_sql methods.

### Input
df : pandas dataframe
index : str : elasticsearch index
type : str : elasticsearch type
EX : 
df.head()
    Name  Age  Weight
0  Kevin   26      94
1   Marc   32      70
2  Louis   35      80

index = 'personnes'

type = 'homme'
### Usage
df.to_elastic(file_path, 'index'=index, 'type'=type)
### Expected Output
{"index":{"_index": "personnes","_type":"homme","_id":1}}
{"fields" : {"Name" : "Kevin","Age" : 26,"Weight" : 94}
{"index" :{"_index": "personnes","_type":"homme","_id":2}}
{"fields" : {"Name" : "Marx","Age" : 32,"Weight" : 70}
{"index" :{"_index": "personnes","_type":"homme","_id":3}}
{"fields" : {"Name" : "Louis","Age" : 35,"Weight" : 80}

