trim whitespace as version

Failed to version parse.

```
# my-app/VERSION
0.0.5
```

```
# my-app/build.gradle
def version = readVersion(file("VERSION"))

android {
    compileSdkVersion 17
    buildToolsVersion '17.0.0'

    defaultConfig {
        versionCode version.toVersionCode()
        versionName version.toVersionName()
        ...
    }   

}
```

```
# stack trace when running gradle task
23:02:19.215 [ERROR] [org.gradle.BuildExceptionReporter] Caused by: java.lang.NumberFormatException: For input string: "5
23:02:19.215 [ERROR] [org.gradle.BuildExceptionReporter] "
23:02:19.216 [ERROR] [org.gradle.BuildExceptionReporter]        at java_lang_Integer$valueOf.call(Unknown Source)
23:02:19.217 [ERROR] [org.gradle.BuildExceptionReporter]        at Version.<init>(/Users/ichigotake/Development/tinyAndroid/ColorfulSweets/gradle/gradle-android-utils/build.gradle:84)
23:02:19.218 [ERROR] [org.gradle.BuildExceptionReporter]        at build_4abl8m0kmbh5pqh453p77iru81$_run_closure5.doCall(/Users/ichigotake/Development/tinyAndroid/ColorfulSweets/gradle/gradle-android-utils/build.gradle:102)
23:02:19.219 [ERROR] [org.gradle.BuildExceptionReporter]        at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:156)
23:02:19.220 [ERROR] [org.gradle.BuildExceptionReporter]        at org.gradle.groovy.scripts.BasicScript.methodMissing(BasicScript.java:79)
23:02:19.221 [ERROR] [org.gradle.BuildExceptionReporter]        at build_4abl8m0kmbh5pqh453p77iru81$_run_closure6.doCall(/Users/ichigotake/Development/tinyAndroid/ColorfulSweets/gradle/gradle-android-utils/build.gradle:107)
23:02:19.223 [ERROR] [org.gradle.BuildExceptionReporter]        at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:156)
23:02:19.223 [ERROR] [org.gradle.BuildExceptionReporter]        at org.gradle.groovy.scripts.BasicScript.methodMissing(BasicScript.java:79)
23:02:19.225 [ERROR] [org.gradle.BuildExceptionReporter]        at build_3oneo5l2nbqbbj5k012lbsbj3v.run(/Users/ichigotake/Development/tinyAndroid/ColorfulSweets/library/build.gradle:3)
23:02:19.226 [ERROR] [org.gradle.BuildExceptionReporter]        at org.gradle.groovy.scripts.internal.DefaultScriptRunnerFactory$ScriptRunnerImpl.run(DefaultScriptRunnerFactory.java:52)
23:02:19.227 [ERROR] [org.gradle.BuildExceptionReporter]        ... 56 more
```