Zijian/change email to description

[BobbyZhouZijian]

fixes #119

Description field should not be empty, should not be blank or start with a blank. should contain only alphenumerical values, commas, periods, question marks or exclamation marks.

[MarcTzh]

Change one parameter, other than that looks good

[codecov-commenter]

Codecov Report

Merging #125 into master will increase coverage by 0.06%.
The diff coverage is 92.15%.

@@             Coverage Diff              @@
##             master     #125      +/-   ##
============================================
+ Coverage     72.31%   72.38%   +0.06%     
  Complexity      400      400              
============================================
  Files            70       70              
  Lines          1228     1231       +3     
  Branches        124      124              
============================================
+ Hits            888      891       +3     
  Misses          308      308              
  Partials         32       32              

Impacted Files	Coverage Δ	Complexity Δ
.../java/seedu/address/logic/commands/AddCommand.java	100.00% <ø> (ø)	8.00 <0.00> (ø)
.../java/seedu/address/model/util/SampleDataUtil.java	20.00% <ø> (ø)	1.00 <0.00> (ø)
src/main/java/seedu/address/ui/TaskCard.java	0.00% <0.00%> (ø)	0.00 <0.00> (ø)
...ain/java/seedu/address/model/task/Description.java	80.00% <80.00%> (ø)	6.00 <6.00> (?)
src/main/java/seedu/address/model/task/Task.java	97.56% <88.88%> (ø)	21.00 <1.00> (ø)
...java/seedu/address/logic/commands/EditCommand.java	97.01% <100.00%> (ø)	12.00 <0.00> (ø)
...a/seedu/address/logic/parser/AddCommandParser.java	100.00% <100.00%> (ø)	5.00 <0.00> (ø)
...ain/java/seedu/address/logic/parser/CliSyntax.java	83.33% <100.00%> (ø)	1.00 <0.00> (ø)
.../seedu/address/logic/parser/EditCommandParser.java	92.85% <100.00%> (+0.54%)	11.00 <0.00> (ø)
...in/java/seedu/address/logic/parser/ParserUtil.java	97.22% <100.00%> (ø)	14.00 <2.00> (ø)
... and 2 more

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[MarcTzh]

One minor comment suggestion, other than that LGTM