Use gradlew for hugo-example (not gradle of OS)

There is a bug when the following tasks are executed:

cleanExample
assembleExample
installExample
In these tasks the gradle of the system is used instead of gradlew.
This leads to strange errors when the two versions are different.

The simple correction consisted on changing the command to execute
from 'gradle to '../gradlew'.

task cleanExample(type: Exec) {
    executable = '../gradlew'
    workingDir = project.file('hugo-example')
    ...
Merge pull request #36 from joninvski/use_top_gradlew

Use gradlew for hugo-example (not gradle of OS)
Lower min_sdk_version to 7 (ECLAIR_MR1)

There is nothing stopping hugo from supporting min_sdk version of 7

`gradlew lint` says ok and the tests on the emulator agree
Merge pull request #37 from joninvski/min_sdk_7

Lower min_sdk_version to 7 (ECLAIR_MR1)
Plugin check should check for extensions too

It is possible to subclass the "android" and "android-library" plugins.
Using "withType" instead of "hasPlugin" will match these plugins.
Merge pull request #41 from klynch/master

Plugin check should check for extensions too