Resolves: OpenST#716
See also: OpenST#718, OpenST#719

Fixes failing test cases after linter error cleanup.
Replaces string usages by Buffer.

  - .gitignore ignores generated files from typescript files.
  - MerklePatriciaProof::verify and MerklePatriciaProof::verifyDebug
    functions uses toData instead of toBytes during comparsion agaist
    value.
  - Improved pattern validity to correctly handle ending branch node.
  - Fixed an issue with branch, extension and leaf nodes
    serialization.
  - .travis.yml runs fuzzy_proof_generator tests.

In addition, contains the followings:

  - Store values in rlp encoding.
  - Introduces sanity tests for FuzzyProofGenerator::generate
    and FuzzyProofGenerator::generateByPattern functions.
  - Adds run.sh script to run FuzzyProofGenerator tests.
  - Updates .travis.yml to run FuzzyProofGenerator tests.

In addition, within './tools/fuzzy_proof_generator_tool/test/run.sh'
tests are disabled as currently failing.

  - Fixes a bug in FuzzyProofGenerator::processExtension() function.

  - Moves Util::encodeCompactExtensionNode() function to
    ExtensionNode::encodeCompact().
  - Moves Util::encodeCompactLeafNode() function to
    LeafNode::encodeCompact().
  - Moves Util::generateRandomKeccak256 function to
    FuzzyProofGenerator::generateRandomKeccak256().
  - Moves nibbles related functionality from Util.ts to NibblesUtil.ts.
  - Removes Util.ts.

  - Improves documentation for low-level bitwise operations
    within NibblesUtil.ts.

  - assert.throws() instances check against a specific error message.
  - Enhances generateByPattern test suites.

  - Fixes lint errors for tools/fuzzy_proof_generator ts files.
  - Checks "proof_generation" dir within `npm run lint`.
  - Disables eslint @typescript-eslint/camelcase" rule.
  - Adds .eslintignore file.

  - Updates dev dependencies within package.json.

  - Renames NibblesUtil to Nibbles.
  - Fixes bugs and stronger requirement checks for
    FuzzyProofGenerator::generateByPattern().
  - Enhances code documentation and comments.