Fixed Pair container class bug (#include statement missing )

* added Pair Test

Change-Id: Icba80051743424bc2ced4c00ce95b2ec7e705dc4
Added offset parameter for 'find' method in String class.

* extended tests too

Change-Id: I54b390f4340df2a6b1dbed5f393fa9fe4a90b266
Added a StringTokenizer class in the utils section.

* added tests

Change-Id: Ief5851aa25463f6a83681d04a3e7554ddc48c068
Fixed consistent formatting without trailing whitespaces.

Change-Id: I39afdea7ab3d9846761f1ddc1f69b1dd77d94c79