Set default startup height and width

[hauchongtang]

Reasons for change

• Seems to affect most mac users
• Initial startup blocking view of panels is a functionality bug

[codecov-commenter]

Codecov Report

Merging #253 (59170ca) into master (3299d3b) will decrease coverage by 0.01%. The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master     #253      +/-   ##
============================================
- Coverage     68.56%   68.55%   -0.02%     
+ Complexity      711      710       -1     
============================================
  Files           112      112              
  Lines          2510     2509       -1     
  Branches        306      305       -1     
============================================
- Hits           1721     1720       -1     
  Misses          677      677              
  Partials        112      112              

Impacted Files	Coverage Δ
src/main/java/seedu/address/ui/MainWindow.java	0.00% <0.00%> (ø)
...u/address/logic/parser/EditStockCommandParser.java	90.90% <0.00%> (-0.40%)	:arrow_down:

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[hauchongtang]

close and use another pr