Fix/remove unneeded dependencies

[DavisVaughan]

Remove:

• curl
• devtools
• readr
• rvest
• stats
• timeSeries
• tseries
• forcats

Move to Suggests:

• scales
• alphavantager
• broom

[codecov]

Codecov Report

Merging #96 into master will decrease coverage by 0.27%.
The diff coverage is 46.66%.

@@            Coverage Diff             @@
##           master      #96      +/-   ##
==========================================
- Coverage   60.65%   60.38%   -0.28%     
==========================================
  Files          16       17       +1     
  Lines        1563     1570       +7     
==========================================
  Hits          948      948              
- Misses        615      622       +7

Impacted Files	Coverage Δ
R/alphavantager.R	0% <0%> (ø)
R/tq_stock_list.R	92.75% <100%> (-0.06%)	⬇️
R/tq_get.R	71.22% <40%> (-0.38%)	⬇️
R/tq_portfolio.R	54.7% <50%> (ø)	⬆️

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