Testing + code coverage

[holgerteichgraeber]

• Addresses Automatic testing #91
• connection to codecov.io : https://codecov.io/gh/holgerteichgraeber/ClustForOpt.jl .
• cleanup of some unused functions
• replaced @error by error(msg). The former is used for logging, whereas the later throws an Exception. We want the latter.

In #91, there are several TODOs concerning which functions still need test coverage. Let's implement them after this PR.

Merging this PR right away, for a reproducible version of the changes and for your comments @YoungFaithful , use #97 .

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (dev@e13cb90). Click here to learn what that means.
The diff coverage is 50%.

@@          Coverage Diff           @@
##             dev      #98   +/-   ##
======================================
  Coverage       ?   64.46%           
======================================
  Files          ?        9           
  Lines          ?      515           
  Branches       ?        0           
======================================
  Hits           ?      332           
  Misses         ?      183           
  Partials       ?        0

Impacted Files	Coverage Δ
src/clustering/run_clust.jl	88.54% <100%> (ø)
src/utils/load_data.jl	71.42% <16.66%> (ø)
src/clustering/extreme_vals.jl	84.21% <33.33%> (ø)
src/utils/utils.jl	83.15% <50%> (ø)
src/utils/datastructs.jl	97.36% <75%> (ø)

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[holgerteichgraeber]

Tests sometimes fail due to memory on travis ( #99 ) , reloading the build seems to be a doable workaround for now,