Fix failing test cases from telegram username

[cshao02]

For #56 #68

Fixed the test cases to account for telegram username in Person class on AddCommand and EditCommand.

All existing test cases now pass.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...java/seedu/address/logic/commands/EditCommand.java	75.00%	0 Missing and 1 partial :warning:

Files with missing lines	Coverage Δ	Complexity Δ
.../seedu/address/logic/parser/EditCommandParser.java	93.33% <100.00%> (+0.74%)	12.00 <0.00> (+1.00)
...in/java/seedu/address/logic/parser/ParserUtil.java	90.00% <ø> (-3.19%)	18.00 <0.00> (+2.00)	:arrow_down:
...java/seedu/address/logic/commands/EditCommand.java	96.51% <75.00%> (-0.93%)	13.00 <0.00> (ø)

... and 1 file with indirect coverage changes

[chuajunyu]

Fix #61