v2.1.0 various stuff

New features:

• Add NERDTree style keymaps for opening files
• Use committer date instead of author date in historyLog
• Allow setting the Merginal window width
• Add option to split vertically/horizontally
• Add merginal_windowSize configuration

Fixes:

• Use exception number instead of string
• Fix try catch to has_key
• Add missing merge commands to mergeConflicts buffer
• Pushing when there are multiple remotes
• Keymaps leaking between buffers
• Add -- after commands to solve branch/path ambiguity
• Fix command running for Vim8 with :terminal support