Add unit tests for apostrophe for WordIterator

These tests mid-word apostrophe, making sure that in English at
least, the apostrophe does act like a quotation mark to break the
word.

Bug: 17641350
Bug: 17673522
Test: adb shell am instrument -w -e class android.text.method.WordIteratorTest com.android.frameworks.coretests/android.support.test.runner.AndroidJUnitRunner
Change-Id: If81df706218bdcd5882ee80905ea2f43786d5412