Fix adstring method

[Aman-Pandey-afk]

Fixing the issue #57

[Aman-Pandey-afk]

@giordano Should I use two lines to implement the change and make a new commit or anything else to overcome this failed codecov check or can this be ignored. Also, feedback on the implementation will be great. (Used absolute function + int cast and sign of dec to correctly mention the signs of string for dec between 0 and -1)

[giordano]

The codecov failure isn't fatal (I believe it detects a fractional decrease of covered lines because there are fewer lines with your change). However you still haven't added a test for the issue this PR is supposed to fix 🙂

[Aman-Pandey-afk]

I added the test mentioned in the issue ( adstring(15, -0.5) ) in the utils-tests.jl and tested it to be passed. I have made it a separate commit as it is for testing purpose (can be merged if needed). Do I need to do anything else (is the codecov skippable or any other advice)? @giordano

[giordano]

Thank you!