I know it's a late answer, but it may help others who encounter a similar issue:
As of recently (Sept. 2015), you are able to upload APKs up to 100 MB if you are targeting Android 2.3 and above - you can read more about it on this help page. Since your app is 90 MB, you should be okay. There is also the Android developers blogspot article explaining the changes here.
Alternatively, or if your app exceeds the 100 MB APK limit, you can use expansion files. These are additional files that are downloaded after your app has installed and can be up to 4 GB (to be specific, you can have two expansion files of up to 2 GB each). You can learn more about expansion files on this page on the Android Developers website.
However, note that there are some limitations to using expansion files, apart from the 2 GB limit per file such as the fact that the user must have downloaded your app through Google Play. More details on these can also be found on the Android Developers page linked above.