write tests for IntervalBuilder when the parsed_lines_enum is in ascending order
start implementing IntervalBuilder ascending
Implement IntervalBuilder each_interval ascending.
Make sure empty interval get created when there are gaps in the logfiles.
Delta aggregator return positive value when newer record hav value greaater than older record.
Remove code duplication for IntervalBuilder#each_interval asc and desc. Implement first in Logfile
last_interval renamed to first_interval and test added for first_interval in ascending order
split ascending/descinding logic into separate modules
Merge branch 'interval_builder_ascending' of github.com:plerohellec/logfile_interval into interval_builder_ascending

Conflicts:
	lib/logfile_interval/interval_builder.rb
split agregator registration code into its own module
add simple aggregator to count number of lines
do not raise exception when logfiles are empty
test that no exception or interval is yielded when logfiles are empty
version 2.0.0
Merge pull request #1 from plerohellec/interval_builder_ascending

Interval builder ascending