v0.15.0: Bump version to 1.15.0

Changes since 1.14.0:

• Implement maktaba#buffer#GetVisualSelection helper (#132).
• Implement maktaba#log#GetFormattedEntries and support 1-arg log handler (see #204).
• Notify user for messages logged at WARN or above by default (#185).
• Fix Syscall.CallAsync failing for complex commands (#205).
• Preserve trailing slash in maktaba#path#Split and MakeRelative (#137 and #175).
• Fix 'maxfuncdepth' error in maktaba#json#Parse corner case (#153).

Bump version to 1.14.0

Changes since 1.13.0:

• Add vim job support to Syscall.CallAsync (#184).
• Add python3 support (#193).
• Enable native JSON support on neovim (#194).

Bump version to 1.13.0

Changes since 1.12.0:

• Syscall.CallAsync improvements (#180, #124, #183).
• Fix maktaba#log# error on reload (#187).

1.12.0: Bump version to 0.12.0

Changes since 0.11.0:
  * Implement maktaba#python#Eval, a polyfill for pyeval that works on
  vim versions older than 7.3.569.
  * Fix maktaba#path#Basename('foo') to return 'foo', not ''.
  * Improve JSON support to handle NaN and Infinity values consistently.
  * Fix IsCallable and IsEnum checking on 7.4.1875 and later.