Shorten `on_experiment...`/`on_repetition...` method names

[HunterMcGushion]

• lambda_callback kwargs dealing with "experiment" and "repetition" time steps have been shortened
  • These four kwargs have been changed to the following values:
    • on_experiment_start -> on_exp_start
    • on_experiment_end -> on_exp_end
    • on_repetition_start -> on_rep_start
    • on_repetition_end -> on_rep_end
• Method names of all other internally-used callbacks have been changed accordingly

[codecov[bot]]

Codecov Report

Merging #149 into master will increase coverage by 1.59%. The diff coverage is 97.58%.

@@            Coverage Diff            @@
##           master    #149      +/-   ##
=========================================
+ Coverage    91.9%   93.5%   +1.59%     
=========================================
  Files          44      44              
  Lines        4363    4375      +12     
=========================================
+ Hits         4010    4091      +81     
+ Misses        353     284      -69

Impacted Files	Coverage Δ
hyperparameter_hunter/utils/general_utils.py	100% <ø> (+35.26%)	:arrow_up:
...ter_hunter/callbacks/wranglers/target_wranglers.py	100% <100%> (ø)	:arrow_up:
hyperparameter_hunter/callbacks/evaluators.py	83.33% <100%> (ø)	:arrow_up:
hyperparameter_hunter/experiments.py	92% <100%> (-0.03%)	:arrow_down:
...parameter_hunter/callbacks/wranglers/predictors.py	100% <100%> (ø)	:arrow_up:
hyperparameter_hunter/callbacks/aggregators.py	98.88% <100%> (ø)	:arrow_up:
...eter_hunter/callbacks/wranglers/input_wranglers.py	100% <100%> (ø)	:arrow_up:
hyperparameter_hunter/callbacks/bases.py	100% <100%> (ø)	:arrow_up:
hyperparameter_hunter/data/data_core.py	97.22% <100%> (ø)	:arrow_up:
...parameter_hunter/data/data_chunks/target_chunks.py	100% <100%> (ø)	:arrow_up:
... and 5 more

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[coveralls]

Pull Request Test Coverage Report for Build 658

• 242 of 248 (97.58%) changed or added relevant lines in 13 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+1.6%) to 93.509%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
hyperparameter_hunter/callbacks/recipes.py	16	22	72.73%
<!--	Total:	242	248	97.58%	-->

Totals
Change from base Build 654:	1.6%
Covered Lines:	4091
Relevant Lines:	4375

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💛 - Coveralls