Rework inline directives

[veelenga]

Closes #234

This work implements the inline directives similar to what eslint implements. The issue can be disabled in the following cases:

1. The line of the reported location ends with ameba:disable_line directive
2. The line above the reported location ends with ameba:disable_next_line directive
3. Any line above the reported location ends with ameba:disable directive (and there is not directive not enable that back)

For example, in all the cases below directive disables the rule:

Time.epoch(1483859302) # ameba:disable_line Style/LargeNumbers

# ameba:disable_next_line Style/LargeNumbers
Time.epoch(1483859302)

# ameba:disable Style/LargeNumbers
Time.epoch(1483859301)
Time.epoch(1483859302)

The rule can be enabled back:

# ameba:disable Style/LargeNumbers
Time.epoch(1483859302)
# ameba:enable Style/LargeNumbers
…

Notes:

• This is a little breaking change for the existed #ameba:disable directive.