Friendly (traceless) error messages

[DannyBen]

This PR comes to improve error messages by showing only the message, and not the trace.

It rescues two exceptions:

• ArgumentError - raised in some cases across the code, for example - when providing an invalid argument to --min-time
• OptionParser::InvalidOption - which is raised when parsing unexpected option
• Closes #61

After merging, you get these:

$ papertrail --min-time asd
Argument Error: Could not parse time string 'asd'

$ papertrail --asd
invalid option: --asd

[lmarburger]

Good addition. I'd be in favor of moving the exception handling behavior out into bin/papertrail in the same way interrupts are handled by adding another rescue clause for those 2 exceptions.

[DannyBen]

Makes sense. Will update the PR later today.

[DannyBen]

@lmarburger - better?

[DannyBen]

Note that in the other bin+lib pairs, there is also some inconsistency.

For example:

1. in the add group lib file, there are rescue statements (which should probably go to the bin, as we did here).
2. To achieve consistent behavior of the different CLI bins, all the bins should probably rescue the same baseline of exceptions (and this code duplication will reduce code quality metrics...).