Remove transaction module

[kevinheavey]

The transaaction module is broken (see #268) and solders.transaction works so I guess we should just use that?

This also entails changing the send_transaction methods such that it is the caller's job to fetch a recent blockhash and sign the transaction

[codecov]

Codecov Report

Attention: Patch coverage is 92.17877% with 14 lines in your changes missing coverage. Please review.

Project coverage is 89.89%. Comparing base (7f2f3cb) to head (37b4b75).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #442      +/-   ##
==========================================
+ Coverage   89.77%   89.89%   +0.12%     
==========================================
  Files          28       27       -1     
  Lines        2210     2118      -92     
==========================================
- Hits         1984     1904      -80     
+ Misses        226      214      -12