Typo fix.

[tmcclintock]

Close some parentheses that weren't closed in CONTRIBUTING.md.

[rpgoldman]

Good catch!

[codecov]

Codecov Report

Merging #3833 into master will decrease coverage by 46.25%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #3833       +/-   ##
===========================================
- Coverage   90.48%   44.23%   -46.26%     
===========================================
  Files         135      135               
  Lines       21113    21113               
===========================================
- Hits        19104     9339     -9765     
- Misses       2009    11774     +9765

Impacted Files	Coverage Δ
pymc3/tests/test_text_backend.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_parallel_sampling.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_modelcontext.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_tuning.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_shared.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_tracetab.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_posdef_sym.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_hdf5_backend.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_util.py	0% <0%> (-100%)	⬇️
pymc3/tests/test_smc.py	0% <0%> (-100%)	⬇️
... and 89 more