Added Foreign key and Added Primary key

[rootrus]

• Once export, it will check the database if there is any foreign key for that specific database and table . If exist then it will format it into migration format and out put as add_fk_to_table.php.
• If columnname id, is primary and auto increment then it will set as $table->id();

Thank you for helping to make this package better!

Please make sure you've read CONTRIBUTING.md before submitting your pull request, and that you have:

• [ ] provided a rationale for your change (I try not to add features that are going to have a limited user-base)
• [ ] used the PSR-2 Coding Standard
• [ ] added tests
• [ ] documented any change in behaviour (e.g. updated the README.md, etc.)
• [ ] only submitted one pull request per feature

Thank you!

[cviebrock]

Sorry it's taken so long to look at this. Would you mind updating your PR to deal with the conflicts above, and then I can merge it and make a new release?

Thanks!

[rootrus]

Sorry for the delay and thank you for the cleanup. Awesome repo! Merry Christmas and happy new year to you and your family!