Upgrade to v0.1.5

[FabijanC]

Usage

• Make responses as similar as possible to those of Alpha 3 testnet (especially in case of rejected transactions).
• Enable transaction signing.
• Enable passing constructor calldata.
• Bump version to v0.1.5

Dev

• Code refactoring:
  • StarknetWrapper is isolated to a separate file (starknet_wrapper.py), and some functions are set to be its methods.
  • Code for adapting function input/output is moved to a separate file (adapt.py):
  • This is probably the biggest influence on this PR's number of changed lines.
• Update TxStatus enumeration in util.py to include all possible statuses.
• Define custom StarknetDevnetException inherited from StarkException
• Improve CLI testing:
  • a new test task is added to config.yml which tests authentication usage
  • contract paths that were previously read from variables in .env are now defined with variables in testing scripts themselves
  • as .env file now serves no purpose, its mention in README.md is removed, as well as .env.example
• Update dependencies.