DEV: Added multiple countries view

[Shivathanu]

Description:

Added option to view multiple countries data in table / chart format.

Instructions:

Multiple countries are input to the cli as below format in order for the data retreival of multiple countries.

Run command:

corona --s country india,ecuador,portugal

Fixes #54

[Shivathanu]

Thanks Luke for taking time to comment on the issue changes, have addressed your comments separately below each one of them.

[rsubtil]

When it is run in minimal/-m mode, it shows duplicated content:

$ corona-cli portugal,spain -m              
  
 #   Country     Cases        Cases (today)   Deaths      Deaths (today)   Recovered    Active       Critical   Per Million 
 →   Worldwide   42,847,157   383,248         1,153,216   4,503            31,602,038   10,091,903   76,918     5,497       
 —                                                                                                                          
  
 #   Country     Cases        Cases (today)   Deaths      Deaths (today)   Recovered    Active       Critical   Per Million 
 →   Worldwide   42,847,157   383,248         1,153,216   4,503            31,602,038   10,091,903   76,918     5,497       
 —                                                                                                                          
 —   Portugal    116,109      3,669           2,297       21               67,842       45,970       221        11,397      
 —   Spain       1,110,372    0               34,752      0                0            1,075,620    2,031      23,746