Adds a few reverse functions

[mewilhel]

Adds the following reverse functions.

log2_rev, log10_rev, exp2_rev, exp10_rev, acos_rev, atan_rev, sinh_rev, cosh_rev, tanh_rev, asinh_rev, acosh_rev, atanh_rev,

[codecov-io]

Codecov Report

Merging #17 into master will decrease coverage by 13.6%. The diff coverage is 0%.

@@             Coverage Diff             @@
##           master      #17       +/-   ##
===========================================
- Coverage   43.94%   30.34%   -13.61%     
===========================================
  Files           7       10        +3     
  Lines         157      234       +77     
===========================================
+ Hits           69       71        +2     
- Misses         88      163       +75

Impacted Files	Coverage Δ
src/IntervalContractors.jl	100% <ø> (ø)
src/hyperbolic.jl	0% <0%> (ø)
src/inverse_hyperbolic.jl	0% <0%> (ø)
src/exponential.jl	0% <0%> (ø)	:arrow_up:
src/inverse_trig.jl	0% <0%> (ø)	:arrow_up:
src/transformations.jl	79.16% <0%> (+4.16%)	:arrow_up:

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[mewilhel]

Will update with tests included.

[dpsanders]

Thanks! There's no need to close the PR just to add tests; just put a label [WIP] in the PR title to show that it's Work In Progress, and hence shouldn't be merged.