Update README.md
Create strings depending on operation. Demo

Create strings only if input is valid at position.
Demo to try creating strings
Fix that a `-` sign is allowed as first character

Change function to allow to put operators at begining of line or not.
Allow input of parentheses

Allow input if applicable of `(` and `)`.
Correct insertion of large string input. (Paste)

It check each character of the paste input one by one to check if it is
valid.
Also if selected a range of characters and put a new input it deletes
the selected area and checks if the new input will be correct.
Delete is always allowed. (Might lead to bugs of deleting something and
having a wrong string to calculate).
Comments for actions and methods.

Added more comments to `GIDACalculateString.m` so it is more clear of
what it is doing.
Solve operations

Solve operations based on strings. This operations can contain:

- '+'

- '-'

- '/'

- '*'

- '(' and ')'

Interface to input characters to a string and validate if the insertion
would create a valid operation. Drawback of this method is, that if the
user made a mistake and forgot to put a number or operator it has to
first add the number and then put the operator.
Documentation update

Updated README.md with usage information of the class.

New names, clrearer names for methods.
Merge pull request #1 from aparedes/Demo

Solve strings, verification of operation strings.
Update README.md
Check if it is a valid string before appending it

Check if the string to be added will create a valid expression, if it
does it will create the new string. If it will not it returns the
original string.
Fix return of original string

When trying to add, if it will not create a valid expression, return
the original string.
Merge pull request #2 from aparedes/master

Minor fixes to stringFrom:withThis:here:
Enables ARC

Use of ARC.
Removes all releases
Merge pull request #5 from aparedes/arc

Enables ARC