Add support for nested calls to apply

[tpgillam]

Support nested calls to apply, by applying all patches in the current environment, as well as those passed to apply.

[codecov]

Codecov Report

Merging #90 (4fe41c2) into master (a1a98dc) will increase coverage by 0.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
+ Coverage   83.87%   84.12%   +0.25%     
==========================================
  Files           6        6              
  Lines         124      126       +2     
==========================================
+ Hits          104      106       +2     
  Misses         20       20              

Impacted Files	Coverage Δ
src/Mocking.jl	45.45% <ø> (ø)
src/patch.jl	100.00% <100.00%> (ø)
src/expr.jl	100.00% <0.00%> (ø)
src/dispatch.jl	100.00% <0.00%> (ø)

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[morris25]

I'm not super familiar with the package but this seems like a useful change.

[oxinabox]

This seems like a pure improvement to me.
Though perhaps should wait for @omus say if there is a problem this causes related to #89
AFAIK they are unrelated.

[omus]

This seems like a pure improvement to me.
Though perhaps should wait for @omus say if there is a problem this causes related to #89
AFAIK they are unrelated.

This doesn't make the problem in #89 any worse so I'm good with that change from that perspective