Added Topics to Collatz Conjecture #870

Added stubs to Matrix #547

complex-numbers: Add topics for exercise to config.json per #873

Add new exercise section to the contributing guide

Added stubs to LargestSeriesProductCalculator

Make changes per review comments

Made class and methods package private

The binary-search tests force the practitioner to generify the class
but only one type (integer) was actually being used in the tests.
This should be changed so that more than one type is actually used, to
make it more clear that generics are necessary and to demonstrate how
generics is used.

As discussed in #230, move linked-list to one of the last difficulty 6
exercises, so that binary-seach is the first exercise that introduces
generics.

Add a hint to the binary-search exercise to explain generics as this
is now the first exercise to require it.

Fixes #230.

* Completes #853

* Add more topics to problem Kindergarten-garden

* Correct the identation

* Correct the identation again

list-ops: add hint of using static methods per #378

wordy: add topics for exercise to config.json per #850

* added topics to perfect numbers

* updated topics

* fixed tabs

Add topics to sum of multiples exercise

Add topics to Secret Handshake exercise

Add topics to transpose exercise

scrabble-score: add topics

Removed recursion

Add topics to pascals-triangle

Triangle: Replace enum with isEquilateral, is Isosceles, and isScalene methods

Add topics to rna-transcription

Re-arrange to put "loops" before "maps".

added diamond topics

added topics to roman numerals

BST: add angle brackets when calling constructor