v0.3.6

JustPIC v0.3.6

Diff since v0.3.5

Merged pull requests:

• Further randomise the location of an injected particle (#117) (@albert-de-montserrat)
• Fix typo in the indexing (#118) (@albert-de-montserrat)
• Add more docs (#119) (@albert-de-montserrat)
• Bump minor version (#121) (@albert-de-montserrat)