DQN Docs and Examples

[lgtm-com[bot]]

This pull request introduces 2 alerts when merging 3bcbcbc34cf9240055be1dec1614df3239016e94 into 471081189c9d764bd46d36aea86b65f999e1163b - view on LGTM.com

new alerts:

• 2 for Unused import

[sampreet-arthi]

Modifying this:

• Adding a DQN tutorial
• Moving the example code here to a tutorial instead

[codecov[bot]]

Codecov Report

Merging #261 into master will increase coverage by 0.03%. The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master     #261      +/-   ##
==========================================
+ Coverage   89.62%   89.65%   +0.03%     
==========================================
  Files          87       87              
  Lines        3748     3752       +4     
==========================================
+ Hits         3359     3364       +5     
+ Misses        389      388       -1     

Impacted Files	Coverage Δ
genrl/agents/deep/base/onpolicy.py	96.42% <ø> (ø)
genrl/agents/deep/dqn/base.py	94.25% <ø> (ø)
genrl/trainers/base.py	88.23% <ø> (ø)
genrl/trainers/onpolicy.py	92.00% <0.00%> (ø)
genrl/agents/deep/a2c/a2c.py	93.42% <100.00%> (ø)
genrl/environments/vec_env/vector_envs.py	92.46% <100.00%> (+0.21%)	:arrow_up:
genrl/trainers/offpolicy.py	91.52% <100.00%> (ø)
genrl/core/noise.py	94.66% <0.00%> (ø)
... and 21 more

[sampreet-arthi]

Merge this? @Sharad24