Allow passing of custom arguments to urllib Request object

[DashLt]

This will allow for more granular control of headers, proxies, and anything else that urllib provides an option for without having to implement the functionality in pySmartDL. Closes #33

[codecov[bot]]

Codecov Report

Merging #34 into master will decrease coverage by 1.49%. The diff coverage is 62.5%.

@@            Coverage Diff            @@
##           master      #34     +/-   ##
=========================================
- Coverage   72.54%   71.05%   -1.5%     
=========================================
  Files           5        5             
  Lines         641      646      +5     
=========================================
- Hits          465      459      -6     
- Misses        176      187     +11

Impacted Files	Coverage Δ
pySmartDL/pySmartDL.py	69.72% <58.33%> (-0.54%)	:arrow_down:
pySmartDL/download.py	71.21% <75%> (+0.62%)	:arrow_up:
pySmartDL/utils.py	69.29% <0%> (-6.3%)	:arrow_down:

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[iTaybb]

Thanks