Revert parser.addoption browser from default ['Chrome'] to default[] as this blocking tests for other browsers to run

[rahulbhave]

There are two locations this change need to be done:
1)
parser.addoption("--browser",
dest="browser",
action="append",
default=['Chrome'],
2) elif metafunc.config.getoption("--browser") == ["Chrome"]:

[rahulbhave]

Fixed the issue:
Below is the PR:
#264 #264

[rahulbhave]

Closing this issue as PR got merged.