Update Metawear-iOSAPI.podspec

Problem is that with this configuration, Cocoapods name the package Metawear-iOSAPI so you have to `#import <Metawear-iOSAPI/MetaWear.h>` and rename all the import in this file :

```
#import <Metawear-iOSAPI/MBLAccelerometer.h>
#import <Metawear-iOSAPI/MBLAccelerometerData.h>
#import <Metawear-iOSAPI/MBLConstants.h>
#import <Metawear-iOSAPI/MBLDeviceInfo.h>
#import <Metawear-iOSAPI/MBLEvent.h>
#import <Metawear-iOSAPI/MBLGPIO.h>
#import <Metawear-iOSAPI/MBLHapticBuzzer.h>
#import <Metawear-iOSAPI/MBLiBeacon.h>
#import <Metawear-iOSAPI/MBLLED.h>
#import <Metawear-iOSAPI/MBLLogEntry.h>
#import <Metawear-iOSAPI/MBLMechanicalSwitch.h>
#import <Metawear-iOSAPI/MBLMetaWear.h>
#import <Metawear-iOSAPI/MBLMetaWearManager.h>
#import <Metawear-iOSAPI/MBLNeopixel.h>
#import <Metawear-iOSAPI/MBLOrientationData.h>
#import <Metawear-iOSAPI/MBLTemperature.h>
#import <Metawear-iOSAPI/MBLTemperatureData.h>
````

Which is just a fucking mess.

So this should fix it.
Also for maintenance you should use an appropriate Pod Template, Code for Cocoapods First

Bisous