This issue is resolved in XCode 6.4 , please update your XCode. If you are still using 6.3 then follow below solution. But I prefere to update Xcode to 6.4.
It is little different ,we have to follow some new procedure.
1) Change your xcodeproj file name first without opening it.
2) Change Target name from Project Editor by double clicking on target name.
![enter image description here](https://i.stack.imgur.com/NZTNO.png)
3) If your project name is not changed yet , you can do it by right side of your xCode as shown in below figure.
![enter image description here](https://i.stack.imgur.com/J3axD.png)
4) You can change plist file name manually.
5) Now for solving scheme issue , you have to remove current scheme and have to add newer scheme with proper name.
![enter image description here](https://i.stack.imgur.com/ei0dt.png)
![enter image description here](https://i.stack.imgur.com/gWkqc.png)
Remove older schemes shown as above(by selecting it and removing by clicking on "-" button) and add newer one(By clicking on "+" button from manage scheme and adding proper name).
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