updated gradle to work on local machine

android-base/build.gradle

@@ -24,6 +24,7 @@ android {
         targetCompatibility JavaVersion.VERSION_1_8
         sourceCompatibility JavaVersion.VERSION_1_8
     }
+    buildToolsVersion '26.0.2'
 }
 
 dependencies {

android-pickers/build.gradle

@@ -18,6 +18,7 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
+    buildToolsVersion '26.0.2'
 }
 
 dependencies {

build.gradle

@@ -5,7 +5,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0-beta6'
+        classpath 'com.android.tools.build:gradle:3.0.0-beta7'
         classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
         classpath 'com.getkeepsafe.dexcount:dexcount-gradle-plugin:0.6.4'
         classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'

uhabits-android/build.gradle

@@ -89,6 +89,7 @@ android {
     sourceSets {
         main.assets.srcDirs += '../uhabits-core/src/main/resources/'
     }
+    buildToolsVersion '26.0.2'
 }
 
 dependencies {