Enhancement/pager teams

[jspaleta]

This PR implements feature request: #38

Note:
using prefix instead of suffix as prefix works better with available single charactger shorthand cmdline arguments.

All logic constrained as part of checkArgs function
team token will be preferred over auth token if team token is available in matching environment variable.

Added initial test of new logic.
Will be adding more tests now.

[jspaleta]

reverted back to suffix... removed the short argument option for both team-name.
Which is fine.. most of the time you'll be using the team name from the annotation support.

[echlebek]

I'd recommend making the naming more consistent between the flags and environment variables. For instance it's --pager-team and PAGERDUTY_TEAM, kind of makes it hard for people to remember. Other than that, looks good!

[jspaleta]

@echlebek fixed in newest commit